merge: Google Kalender som menupunkt, med Verdandes egen kalender lagt over

Læs bredt, skriv snævert — decision 5 i planen, og kun den første halvdel: kalenderen læses, og der skrives ingenting tilbage. **OAuth-blokeringen er reel og blev ikke gået udenom.** En klient registreret som *Internal* tager kun konti i sit eget workspace — også til kalendere, ikke kun Gmail. Andreas' private konto bliver afvist med `org_internal`, og det er klienten, der virker efter hensigten, ikke en fejl. Fladen siger det nu med ord, man kan handle på, frem for at vise Googles egen skærm, der ikke gør. Vejen udenom, som ikke er bygget: kalenderens egen hemmelige ICS-adresse. Ingen OAuth, virker for enhver konto, og `internal/ics` findes allerede. Det er det næste stykke, og det eneste, der låser den private konto op. `internal/google` er flyttet ud af `internal/gmail`, fordi de to er det samme flow, der er uenige om én streng. Egen callback-adresse frem for at dele Gmails: én callback, der finder ud af hvilken token-butik den skal skrive i, går galt ved at overskrive en Gmail-forbindelse, der virkede. Egne tabeller frem for `mailboxes`. `trigger_kind`, `seen` og `last_uid` svarer alle på "hvad gør en besked til en opgave", og ingenting her bliver til en opgave; én konto har mange kalendere, og `mailboxes` har ikke plads til en en-til-mange. Afgørende i praksis: `mailboxes.kind` har en CHECK, og SQLite kan ikke ændre en — en tredje værdi koster den tabelombygning, som migration 0021 skulle igennem. Begivenheder erstattes pr. kalender pr. vindue frem for at flettes med et sync-token: et vindue, der slettes og skrives forfra, kan ikke komme ud af trit, og et sync-token er endnu en ting, der skal være rigtig for altid, for at gitteret ikke stille viser noget forkert. `CalendarView` er udvidet, ikke kopieret. En begivenhed er et fyldt bånd, hvor en opgave er et kort med en farvet kant, så de to læses forskelligt før et ord er læst — og den kan ikke trækkes og er aldrig en knap: der er ikke noget at gøre færdigt ved en andens møde. To værn på det, der kommer fra Google: farven skal matche et hex-mønster, før den må stå i en style, og linket bliver kun til et href, hvis det begynder med https. Konflikten i jobs.go var to nye jobs skrevet på samme linje. Begge skal med. Co-Authored-By: Claude Opus 5 <[email protected]>
docs(web): registreringsteksten fortæller nu, at klienten dækker begge dele
2026-08-20 07:39:12 +02:00 · 2026-08-20 07:33:24 +02:00 · 2026-08-20 07:30:55 +02:00 · 2026-08-20 07:27:42 +02:00 · 2026-08-20 07:24:01 +02:00 · 2026-08-20 07:22:25 +02:00
34 changed files with 4294 additions and 365 deletions
@@ -103,15 +103,16 @@ Apple Reminders, forward mail into it, and add it to Claude as a connector.
 | Mail-to-task | Done, tested |
 | AI layer (Anthropic/OpenAI/Google/local) | Built, degrades when unconfigured |
 | Gmail: OAuth2 with PKCE, polling, one-way to tasks | Done, tested |
+| Google Calendar: read-only, laid over the task calendar | Built, never run against Google |
 | Update notice for administrators | Done, tested |
 | Personal API tokens | Done, tested |
 | OpenAPI 3.1 spec, checked against the router | Done, tested |
 | End-to-end smoke tests (Playwright) | Done |
 | Documentation, landing page, licence | Done |

-**Not finished:** Web Push, the AI providers and the Gmail API calls are
-implemented against their specifications and have only ever been exercised there,
-not against live services. Everything else has an interface: opening a task shows
+**Not finished:** Web Push, the AI providers, and the Gmail and Google Calendar
+API calls are implemented against their specifications and have only ever been
+exercised there, not against live services. Everything else has an interface: opening a task shows
 its description, sub-tasks, comments, files and reminders, and the settings pages
 cover the account, notifications, integrations, AI, API tokens, import, export and
 templates.
@@ -75,6 +75,7 @@ func run() error {
 	runner := jobs.New(cfg, db, log, api.Mail(), api.Hub())
 	runner.SyncGmail = api.SyncGmail
 	runner.SyncMailbox = api.SyncMailbox
+	runner.SyncCalendars = api.SyncCalendars
 	runner.Push = api.PushToUser
 	runner.SendBeacon = api.SendBeacon
 	runner.Start(jobCtx)
@@ -1,13 +1,14 @@
 # Calendar and CalDAV

-Two ways to get your tasks into a calendar, and they are not the same thing.
+Two ways to get your tasks into a calendar, one way to get a calendar into
+verdande, and none of the three is the same thing.

-| | [Feed](#subscribing-to-a-feed) | [CalDAV](#connecting-a-caldav-client) |
-|---|---|---|
-| Direction | Read only | Two-way |
-| Works with | Anything that subscribes to a URL | Apple Reminders, Thunderbird, DAVx⁵ |
-| You can tick things off | No | Yes |
-| Setup | Paste a URL | Username and token |
+| | [Feed](#subscribing-to-a-feed) | [CalDAV](#connecting-a-caldav-client) | [Google Calendar](#showing-a-google-calendar-in-verdande) |
+|---|---|---|---|
+| Direction | Tasks out, read only | Tasks out, two-way | Events **in**, read only |
+| Works with | Anything that subscribes to a URL | Apple Reminders, Thunderbird, DAVx⁵ | A Google account |
+| You can tick things off | No | Yes | No — an event is not a task |
+| Setup | Paste a URL | Username and token | Connect, then pick calendars |

 ## Subscribing to a feed

@@ -39,6 +40,42 @@ most people actually keep.
    **Settings → Calendar feed → Rotate** issues a new one and breaks the old
    immediately.

+## Showing a Google calendar in verdande
+
+The two sections above send your tasks *out*. This is the other direction: your
+Google calendar drawn underneath them, so one screen answers "what does this day
+already have in it".
+
+**Settings → Integrations → Google Calendar → Connect**, then tick the calendars
+you want and press Save. They appear in **Calendar** in the sidebar, in Google's
+own colour for each one, beside your own tasks with due dates.
+
+It needs the same OAuth client Gmail uses, with the Calendar API enabled and the
+second redirect URI registered — see [Configuration](configuration.md#google).
+
+!!! warning "Read only"
+    verdande never writes to your Google calendar. An event cannot be dragged,
+    edited or ticked off here; clicking one opens it in Google, which is where it
+    can be changed. Your own tasks in the same grid still drag to another day as
+    they always have.
+
+    Writing would need the `calendar.events` scope and an answer to what should
+    happen when both sides moved the same meeting — which is a synchronisation
+    model rather than a scope, and it is deliberately not built yet.
+
+!!! note "The Internal client applies here too"
+    An OAuth client registered as *Internal* in a Google Workspace can only be
+    used by accounts in that workspace, calendars included. A personal
+    `@gmail.com` address is refused with `org_internal`. For one personal account
+    the shorter road is the calendar's own secret address: in Google Calendar,
+    **Settings → the calendar → Integrate calendar → Secret address in iCal
+    format**. Nothing in verdande subscribes to one yet — it is the next piece of
+    this feature.
+
+Events are kept for ninety days back and a year forward, refreshed every fifteen
+minutes and whenever you press **Fetch now**. Paging the grid past that window
+says so rather than showing an empty month.
+
 ## Connecting a CalDAV client

 This is the one where ticking something off in Apple Reminders ticks it off here.
@@ -39,12 +39,24 @@ Any Go duration: `720h`, `30m`, `45s`.
    yourself, password resets are written to the log, and reminders arrive in the
    app and as Web Push rather than by email.

-## Gmail
+## Google

-Only needed if anyone will connect a mailbox. Register an OAuth client in Google
-Cloud (**APIs & Services → Credentials → OAuth client ID → Web application**) with
-the redirect URI `https://your-address/oauth/gmail/callback`, enable the Gmail API,
-and add the `gmail.readonly` scope.
+Only needed if anyone will connect a Gmail mailbox or a Google calendar. One
+registration covers both: register an OAuth client in Google Cloud
+(**APIs & Services → Credentials → OAuth client ID → Web application**) and add
+**both** redirect URIs:
+
+```
+https://your-address/oauth/gmail/callback
+https://your-address/oauth/calendar/callback
+```
+
+Then enable the APIs and scopes for whichever you want:
+
+| For | Enable | Scope |
+|---|---|---|
+| Mailboxes | Gmail API | `gmail.readonly` |
+| Calendar | Google Calendar API | `calendar.readonly` |

 | Variable | What it does |
 |---|---|
@@ -52,8 +64,15 @@ and add the `gmail.readonly` scope.
 | `VERDANDE_GMAIL_CLIENT_SECRET` | The client secret. |

 One registration serves every user on the instance; each person authorises their
-own mailbox from **Settings → Gmail**. The redirect URI is derived from
-`VERDANDE_BASE_URL`, so it cannot drift out of step with what you registered.
+own mailbox from **Settings → Integrations → Gmail** and their own calendar from
+**Settings → Integrations → Google Calendar**. Both redirect URIs are derived from
+`VERDANDE_BASE_URL`, so they cannot drift out of step with what you registered.
+
+!!! note "Two connections, two grants"
+    Connecting a calendar does not disturb a working Gmail connection, and
+    disconnecting one does not take the other with it. Google issues a refresh
+    token per authorisation and keeps up to a hundred of them live per account,
+    each carrying only the scopes it was granted with.

 ## Secrets

@@ -16,7 +16,7 @@ administrator who can read yours.
 **Settings → Integrations → Gmail → Connect.**

 Gmail needs an OAuth client, which is the instance's registration with Google
-rather than anybody's account — see [Configuration](configuration.md#gmail).
+rather than anybody's account — see [Configuration](configuration.md#google).
 Once it is set up, each person connects their own mailbox through it.

 Choose what makes a task:
@@ -2654,6 +2654,126 @@ paths:
                  created: { type: integer }
        "502": { $ref: "#/components/responses/Upstream" }

+  /api/v1/calendar:
+    get:
+      tags: [integrations]
+      summary: The Google Calendar connection and the calendars in it.
+      description: |
+        Read-only. verdande shows a Google calendar beside its own dated tasks and
+        never writes one back — writing needs the `calendar.events` scope and an
+        answer to what happens when both sides moved the same meeting, which is a
+        synchronisation model rather than a scope.
+
+        The list of calendars is fetched from Google when it is empty, so an
+        account that connected during a hiccup corrects itself on the next look
+        rather than showing an empty panel for ever.
+      responses:
+        "200": { $ref: "#/components/responses/Calendar" }
+    delete:
+      tags: [integrations]
+      summary: Disconnect the calendar and forget its tokens.
+      description: >
+        The cached events go too. Unlike the tasks a mailbox made, none of this is
+        the person's own work — it is a copy of somebody else's calendar, and it
+        means nothing without the account.
+      responses:
+        "204": { description: Disconnected. }
+
+  /api/v1/calendar/calendars:
+    put:
+      tags: [integrations]
+      summary: Choose which calendars are drawn.
+      description: >
+        The whole set in one write rather than one flip at a time, for the reason
+        the projects' order is written the same way: the question is "these ones",
+        and a list built out of several requests can land half applied. A calendar
+        turned off has its cached events removed; they come back if it is turned
+        on again.
+      requestBody:
+        required: true
+        content:
+          application/json:
+            schema:
+              type: object
+              properties:
+                shown:
+                  type: array
+                  items: { type: string }
+      responses:
+        "204": { description: Saved. }
+        "404": { $ref: "#/components/responses/NotFound" }
+
+  /api/v1/calendar/authorize:
+    post:
+      tags: [integrations]
+      summary: Begin the OAuth flow for a calendar.
+      description: |
+        The same registration Gmail signs in through, asking for
+        `calendar.readonly` and coming back to `/oauth/calendar/callback`. Google
+        issues a refresh token per authorisation, so connecting a calendar does not
+        disturb a working Gmail connection.
+      responses:
+        "200":
+          description: OK
+          content:
+            application/json:
+              schema:
+                type: object
+                properties:
+                  url: { type: string }
+        "409":
+          $ref: "#/components/responses/Conflict"
+
+  /api/v1/calendar/sync:
+    post:
+      tags: [integrations]
+      summary: Refresh the chosen calendars now.
+      description: >
+        Refreshes the list of calendars and replaces the cached window of events
+        for the ones that are shown. `partial` means the budget ran out before the
+        last calendar; what was read is kept, and the rest arrive on the next run.
+      responses:
+        "200":
+          description: OK
+          content:
+            application/json:
+              schema:
+                type: object
+                properties:
+                  events: { type: integer }
+                  partial: { type: boolean }
+        "502": { $ref: "#/components/responses/Upstream" }
+
+  /api/v1/calendar/events:
+    get:
+      tags: [integrations]
+      summary: The events of the chosen calendars, between two days.
+      description: |
+        Both ends inclusive, and an event that merely overlaps the range comes
+        back — a grid asks which cells an event covers, not where it begins.
+
+        `from` and `to` in the answer are the window verdande holds a copy of,
+        which is not the window that was asked for. A grid paged past it gets no
+        events, and an empty answer with no explanation is a calendar quietly
+        claiming a day is clear.
+      parameters:
+        - { name: from, in: query, required: true, schema: { type: string, format: date } }
+        - { name: to, in: query, required: true, schema: { type: string, format: date } }
+      responses:
+        "200":
+          description: OK
+          content:
+            application/json:
+              schema:
+                type: object
+                properties:
+                  events:
+                    type: array
+                    items: { $ref: "#/components/schemas/CalendarEvent" }
+                  from: { type: string, format: date }
+                  to: { type: string, format: date }
+        "422": { $ref: "#/components/responses/Validation" }
+
  /api/v1/export/notes.zip:
    get:
      tags: [notes]
@@ -3297,6 +3417,26 @@ paths:
      responses:
        "302": { description: "Back into the app, with the outcome as a query parameter." }

+  /oauth/calendar/callback:
+    get:
+      tags: [integrations]
+      summary: Where Google sends the browser after consent to a calendar.
+      description: |
+        A URI of its own rather than a reuse of Gmail's. One callback deciding from
+        stored state which of the two flows had come back would put the choice of
+        which token store to write behind a lookup — and when that goes wrong it
+        goes wrong by overwriting a working Gmail connection with calendar tokens.
+
+        Answers with a redirect to `/indstillinger/integrationer`, not with JSON.
+        An `org_internal` error here means the OAuth app is registered as Internal
+        and the account is outside the organisation.
+      parameters:
+        - { name: code, in: query, schema: { type: string } }
+        - { name: state, in: query, schema: { type: string } }
+        - { name: error, in: query, schema: { type: string } }
+      responses:
+        "302": { description: "Back into the app, with the outcome as a query parameter." }
+
  /mcp:
    post:
      tags: [integrations]
@@ -3479,6 +3619,40 @@ components:
              email: { type: string }
              trigger: { type: string, enum: ["", starred, label, both] }
              label: { type: string }
+    Calendar:
+      description: OK
+      content:
+        application/json:
+          schema:
+            type: object
+            properties:
+              connected: { type: boolean }
+              account:
+                type: string
+                description: >
+                  The address of the connected account, taken from the id of its
+                  primary calendar — which is where Google puts it, so no profile
+                  scope has to be asked for to learn it.
+              read_only:
+                type: boolean
+                description: >
+                  Always true today. Stated rather than assumed: an interface that
+                  quietly looks editable is one somebody will try to edit.
+              has_client:
+                type: boolean
+                description: >
+                  Whether an OAuth client is registered on this instance at all, so
+                  the page can explain rather than offer a button that answers 409.
+              redirect_uri:
+                type: string
+                description: >
+                  What has to be registered with Google, spelled out. Derived from
+                  VERDANDE_BASE_URL and matched exactly — the single most likely
+                  thing to be wrong, and the error Google gives names neither value.
+              last_sync_at: { type: string, format: date-time }
+              calendars:
+                type: array
+                items: { $ref: "#/components/schemas/Calendar" }
    ImportResult:
      description: Created
      content:
@@ -3496,6 +3670,62 @@ components:
                items: { type: string }

  schemas:
+    Calendar:
+      type: object
+      description: >
+        One calendar inside a connected account. Kept whether or not it is shown,
+        so turning one off and on again gives back the same row.
+      properties:
+        id: { type: string }
+        remote_id: { type: string, description: "The id Google knows it by; an address for the primary calendar." }
+        name: { type: string }
+        colour:
+          type: string
+          description: >
+            Google's own hex value, not one of verdande's ten named colours. Those
+            are names so the interface can restyle them per theme and they are
+            verdande's palette; a Google calendar is told apart by the colour the
+            person already knows it by.
+        time_zone: { type: string }
+        primary: { type: boolean }
+        writable:
+          type: boolean
+          description: >
+            Whether the connected account could write to it. Nothing does — the
+            scope is read-only — and it is stored so the day something can, the
+            interface knows which calendars could even be offered.
+        shown: { type: boolean }
+
+    CalendarEvent:
+      type: object
+      description: >
+        One occurrence, in the shape a grid asks about. A recurrence is expanded by
+        Google into its occurrences, so what arrives here is a day, not a rule.
+      properties:
+        id: { type: string }
+        calendar_id: { type: string }
+        summary: { type: string }
+        starts_at:
+          type: string
+          description: >
+            RFC 3339 as Google wrote it, offset and all. Empty for an all-day
+            event, which has a day rather than a moment — inventing midnight for it
+            is how an event moves a day when a container moves time zone.
+        ends_at: { type: string }
+        start_day: { type: string, format: date }
+        end_day:
+          type: string
+          format: date
+          description: >
+            The last day the event covers, inclusive. Google's all-day end date is
+            exclusive and is corrected on the way in, once, rather than by every
+            reader.
+        all_day: { type: boolean }
+        location: { type: string }
+        url: { type: string, description: "Opens the event in Google's own interface." }
+        calendar_name: { type: string }
+        colour: { type: string }
+
    Note:
      type: object
      description: A page of Markdown. The body is the stored form and the exported form.
@@ -59,10 +59,19 @@ type Config struct {
 	// without spending the real one on every run.
 	GmailSyncBudget time.Duration

-	// GmailEndpoints redirects the Gmail calls at a server the tests control. Empty
-	// in production, where it means Google.
-	GmailTokenURL string
-	GmailAPIURL   string
+	// CalendarSyncBudget is the same bound for one calendar refresh, and exists for
+	// the same reason: a slow Google held the request open past what Cloudflare is
+	// willing to wait, and the browser got Cloudflare's HTML instead of an error
+	// this server could explain.
+	CalendarSyncBudget time.Duration
+
+	// Where Google is. Empty in production; a test points them at a server it
+	// controls, which is the only way to exercise a Google that is slow or refuses.
+	// The token endpoint is shared — Gmail and Calendar sign in through the same
+	// registration — and the two APIs are not.
+	GoogleTokenURL string
+	GmailAPIURL    string
+	CalendarAPIURL string

 	PanelURL      string
 	PanelToken    string
@@ -98,14 +107,15 @@ func Load() (*Config, error) {
 		TrashRetention: 30 * 24 * time.Hour,
 		Dev:            envBool("VERDANDE_DEV", false),

-		GmailClientID:     env("VERDANDE_GMAIL_CLIENT_ID", ""),
-		GmailSyncBudget:   25 * time.Second,
-		PanelURL:          strings.TrimSuffix(env("VERDANDE_PANEL_URL", ""), "/"),
-		PanelToken:        env("VERDANDE_PANEL_TOKEN", ""),
-		PanelServerID:     env("VERDANDE_PANEL_SERVER_ID", ""),
-		GmailClientSecret: env("VERDANDE_GMAIL_CLIENT_SECRET", ""),
-		SecretKey:         env("VERDANDE_SECRET_KEY", ""),
-		UpdateCheck:       envBool("VERDANDE_UPDATE_CHECK", false),
+		GmailClientID:      env("VERDANDE_GMAIL_CLIENT_ID", ""),
+		GmailSyncBudget:    25 * time.Second,
+		CalendarSyncBudget: 25 * time.Second,
+		PanelURL:           strings.TrimSuffix(env("VERDANDE_PANEL_URL", ""), "/"),
+		PanelToken:         env("VERDANDE_PANEL_TOKEN", ""),
+		PanelServerID:      env("VERDANDE_PANEL_SERVER_ID", ""),
+		GmailClientSecret:  env("VERDANDE_GMAIL_CLIENT_SECRET", ""),
+		SecretKey:          env("VERDANDE_SECRET_KEY", ""),
+		UpdateCheck:        envBool("VERDANDE_UPDATE_CHECK", false),
 	}

 	var err error
@@ -152,6 +162,15 @@ func (c *Config) BackupsDir() string { return filepath.Join(c.DataDir, "backups"
 // configured separately and left to drift out of step with it.
 func (c *Config) GmailRedirectURL() string { return c.BaseURL + "/oauth/gmail/callback" }

+// CalendarRedirectURL is a second registered URI rather than a reuse of Gmail's.
+//
+// One callback that decided from server-side state which of the two flows had come
+// back would save the operator one line in Google Cloud, and would put the choice
+// of *which token store to write* behind a lookup. When that goes wrong it goes
+// wrong by overwriting a working Gmail connection with calendar tokens — a failure
+// nobody would think to look for. Two paths cannot do that.
+func (c *Config) CalendarRedirectURL() string { return c.BaseURL + "/oauth/calendar/callback" }
+
 func env(key, def string) string {
 	if v, ok := os.LookupEnv(key); ok && v != "" {
 		return v
@@ -0,0 +1,339 @@
+// Package gcal reads a Google Calendar. It never writes one.
+//
+// The scope is calendar.readonly, and that is the whole of the decision: verdande
+// already is a CalDAV server, so a Google event shown here is a second calendar
+// laid over the first, not a copy Google and verdande now both have to agree
+// about. Writing needs `calendar.events`, and it needs an answer to what happens
+// when both sides moved the same meeting — which is a synchronisation model, not a
+// scope. Read first; write later and to one calendar at a time.
+//
+// What the API gives back and what this returns are deliberately different shapes.
+// Google answers with RFC 3339 instants for a timed event and bare dates for an
+// all-day one, and with an *exclusive* end date for the second. A calendar grid
+// asks one question — "which cells does this event cover" — so that is what an
+// Event answers, in days, worked out once here rather than in every caller.
+package gcal
+
+import (
+	"context"
+	"fmt"
+	"net/http"
+	"net/url"
+	"strings"
+	"time"
+
+	"github.com/kristianwind/verdande/internal/google"
+)
+
+// Scope is read-only, and only the calendar.
+//
+// Google also offers calendar.calendarlist.readonly and calendar.events.readonly,
+// which together are strictly less than this — they leave out access rules and
+// account settings, which verdande has no use for. They are the tighter pair and
+// worth moving to; they are also newer, and this one has been documented and
+// accepted unchanged for a decade. A consent screen that fails with `invalid_scope`
+// is not a place to be adventurous on somebody else's Google account.
+const Scope = "https://www.googleapis.com/auth/calendar.readonly"
+
+const defaultAPIBase = "https://www.googleapis.com/calendar/v3"
+
+// The OAuth flow, which is Google's rather than the calendar's — the same one
+// Gmail signs in through, asking for the scope above. Aliased so a caller reads
+// one package for one feature.
+type (
+	Config = google.Config
+	PKCE   = google.PKCE
+	Token  = google.Token
+)
+
+var NewPKCE = google.NewPKCE
+
+// ErrUnauthorized means the tokens are no longer good — access was revoked, or the
+// password changed. Re-exported so a caller need not know the flow lives elsewhere.
+var ErrUnauthorized = google.ErrUnauthorized
+
+type Client struct {
+	accessToken string
+	// base is where the Calendar API is. A field rather than a constant so a test
+	// can point it at a server it controls; empty is Google. There is no other way
+	// to exercise a calendar that is slow, empty, or refuses.
+	base string
+	http *http.Client
+}
+
+func NewClient(accessToken string) *Client {
+	return &Client{accessToken: accessToken, http: &http.Client{Timeout: 30 * time.Second}}
+}
+
+// At points the client at another server. Tests only; the zero value is Google.
+func (c *Client) At(base string) *Client {
+	c.base = base
+	return c
+}
+
+func (c *Client) api() string {
+	if c.base != "" {
+		return c.base
+	}
+	return defaultAPIBase
+}
+
+// Calendar is one entry in the person's calendar list.
+type Calendar struct {
+	ID string
+	// Name is the summary Google holds. A calendar somebody renamed for themselves
+	// carries summaryOverride instead, and that is the name they will look for.
+	Name string
+	// Colour is Google's own hex value for the calendar, which is what makes two
+	// calendars in one grid tellable apart. Their own colour rather than one picked
+	// here: it is the colour they already know the calendar by.
+	Colour   string
+	TimeZone string
+	Primary  bool
+	// Owner means the connected account can write to it. Nothing writes today —
+	// it is stored so the day something does, the interface knows which calendars
+	// could even be offered.
+	Owner bool
+}
+
+// Calendars lists what the connected account can see.
+func (c *Client) Calendars(ctx context.Context) ([]Calendar, error) {
+	var out []Calendar
+	page := ""
+	// Bounded rather than "until Google stops": a page token that never empties is
+	// a loop that never ends, and the difference between a bug at Google and a
+	// hung sync should not be this server hanging.
+	for range 10 {
+		v := url.Values{}
+		v.Set("minAccessRole", "reader")
+		v.Set("maxResults", "250")
+		if page != "" {
+			v.Set("pageToken", page)
+		}
+
+		var parsed struct {
+			Items []struct {
+				ID              string `json:"id"`
+				Summary         string `json:"summary"`
+				SummaryOverride string `json:"summaryOverride"`
+				BackgroundColor string `json:"backgroundColor"`
+				TimeZone        string `json:"timeZone"`
+				Primary         bool   `json:"primary"`
+				AccessRole      string `json:"accessRole"`
+				Deleted         bool   `json:"deleted"`
+			} `json:"items"`
+			NextPageToken string `json:"nextPageToken"`
+		}
+		if err := c.get(ctx, c.api()+"/users/me/calendarList?"+v.Encode(), &parsed); err != nil {
+			return nil, err
+		}
+
+		for _, item := range parsed.Items {
+			if item.Deleted {
+				continue
+			}
+			name := item.SummaryOverride
+			if name == "" {
+				name = item.Summary
+			}
+			out = append(out, Calendar{
+				ID: item.ID, Name: name, Colour: item.BackgroundColor,
+				TimeZone: item.TimeZone, Primary: item.Primary,
+				Owner: item.AccessRole == "owner" || item.AccessRole == "writer",
+			})
+		}
+		if parsed.NextPageToken == "" {
+			break
+		}
+		page = parsed.NextPageToken
+	}
+	return out, nil
+}
+
+// Event is one occurrence, in the shape a calendar grid asks about.
+type Event struct {
+	ID      string
+	Summary string
+	// StartsAt and EndsAt are RFC 3339 for a timed event and empty for an all-day
+	// one — an all-day event has no instant, only a day, and inventing midnight for
+	// it is how an event moves a day every time a server changes time zone.
+	StartsAt string
+	EndsAt   string
+	// StartDay and EndDay are the first and last day the event covers, inclusive at
+	// both ends. Google's all-day end date is exclusive; that is corrected here,
+	// once, rather than in every reader.
+	StartDay string
+	EndDay   string
+	AllDay   bool
+	Location string
+	// URL opens the event in Google's own interface. Same reasoning as the Gmail
+	// link on a task made from a mail: what verdande shows is a pointer to the
+	// event, not a second copy of it that somebody could try to edit.
+	URL string
+}
+
+// Events lists what falls inside a window, one calendar at a time.
+//
+// `singleEvents` expands a recurrence into its occurrences, which is the only form
+// a grid can draw: an RRULE is an instruction, and a Tuesday cell needs the Tuesday
+// it produced. It also means verdande does not have to grow a second recurrence
+// engine that agrees with Google's about Danish summer time.
+//
+// from and to are dates, inclusive. The window is the caller's business; this
+// turns it into the half-open interval Google wants.
+func (c *Client) Events(ctx context.Context, calendarID, from, to string) ([]Event, error) {
+	start, err := time.Parse(dateLayout, from)
+	if err != nil {
+		return nil, fmt.Errorf("gcal: from: %w", err)
+	}
+	end, err := time.Parse(dateLayout, to)
+	if err != nil {
+		return nil, fmt.Errorf("gcal: to: %w", err)
+	}
+
+	var out []Event
+	page := ""
+	for range 20 {
+		v := url.Values{}
+		v.Set("singleEvents", "true")
+		v.Set("orderBy", "startTime")
+		v.Set("maxResults", "2500")
+		// UTC, and a day of slack at each end. An event at 23:30 on the last day in
+		// Copenhagen is 21:30 UTC that day, but one at 00:30 on the first day is
+		// 22:30 UTC the day *before* — so a window cut exactly at the requested
+		// dates loses the events at both edges. The extra day is thrown away again
+		// by the day fields below, which are computed from the event's own offset.
+		v.Set("timeMin", start.AddDate(0, 0, -1).Format(time.RFC3339))
+		v.Set("timeMax", end.AddDate(0, 0, 2).Format(time.RFC3339))
+		if page != "" {
+			v.Set("pageToken", page)
+		}
+
+		var parsed struct {
+			Items         []rawEvent `json:"items"`
+			NextPageToken string     `json:"nextPageToken"`
+		}
+		url := c.api() + "/calendars/" + url.PathEscape(calendarID) + "/events?" + v.Encode()
+		if err := c.get(ctx, url, &parsed); err != nil {
+			return nil, err
+		}
+
+		for _, item := range parsed.Items {
+			// A cancelled occurrence of a recurring event still comes back, so that
+			// a client keeping its own copy knows to drop it. verdande replaces the
+			// window wholesale, so it only has to not add it.
+			if item.Status == "cancelled" {
+				continue
+			}
+			event, ok := item.event()
+			if !ok {
+				continue
+			}
+			if event.EndDay < from || event.StartDay > to {
+				continue // the slack above, thrown away
+			}
+			out = append(out, event)
+		}
+		if parsed.NextPageToken == "" {
+			break
+		}
+		page = parsed.NextPageToken
+	}
+	return out, nil
+}
+
+const dateLayout = "2006-01-02"
+
+type rawEvent struct {
+	ID       string `json:"id"`
+	Status   string `json:"status"`
+	Summary  string `json:"summary"`
+	Location string `json:"location"`
+	HTMLLink string `json:"htmlLink"`
+	Start    when   `json:"start"`
+	End      when   `json:"end"`
+}
+
+type when struct {
+	Date     string `json:"date"`
+	DateTime string `json:"dateTime"`
+}
+
+// event turns Google's two shapes into the one a grid can read.
+//
+// The second return is false for an event with neither a date nor a dateTime —
+// which Google does return, for an event somebody is still being asked about. It
+// belongs on no day, so there is no cell to draw it in.
+func (r rawEvent) event() (Event, bool) {
+	e := Event{
+		ID: r.ID, Summary: strings.TrimSpace(r.Summary),
+		Location: r.Location, URL: r.HTMLLink,
+	}
+	if e.Summary == "" {
+		// Google's own interface says this for an event with no title, and a blank
+		// chip in a grid reads as a rendering fault rather than as an empty title.
+		e.Summary = "(uden titel)"
+	}
+
+	switch {
+	case r.Start.Date != "":
+		e.AllDay = true
+		e.StartDay = r.Start.Date
+		// Google's all-day end is the day *after* the last one, so a one-day event
+		// ends tomorrow. Subtracting a day is what makes "covers this cell" a
+		// comparison rather than a special case at every call site.
+		e.EndDay = r.Start.Date
+		if day, err := time.Parse(dateLayout, r.End.Date); err == nil {
+			if last := day.AddDate(0, 0, -1); !last.Before(mustDay(r.Start.Date)) {
+				e.EndDay = last.Format(dateLayout)
+			}
+		}
+	case r.Start.DateTime != "":
+		e.StartsAt = r.Start.DateTime
+		e.EndsAt = r.End.DateTime
+		// The day is the date part of the timestamp Google returned, which carries
+		// the event's own offset. Parsing it into a time.Time and formatting it
+		// back would ask *this process* what day it is — and a container running in
+		// UTC would then move a 23:30 meeting in Copenhagen to the day before.
+		e.StartDay = dayOf(r.Start.DateTime)
+		e.EndDay = dayOf(r.End.DateTime)
+		if e.EndDay == "" {
+			e.EndDay = e.StartDay
+		}
+		// An event ending at midnight ends the evening before, as far as a grid is
+		// concerned. Without this, every meeting that runs to 24:00 puts a chip in
+		// the following day as well.
+		if e.EndDay > e.StartDay && strings.Contains(r.End.DateTime, "T00:00:00") {
+			if day, err := time.Parse(dateLayout, e.EndDay); err == nil {
+				e.EndDay = day.AddDate(0, 0, -1).Format(dateLayout)
+			}
+		}
+	default:
+		return Event{}, false
+	}
+	if e.EndDay < e.StartDay {
+		e.EndDay = e.StartDay
+	}
+	return e, true
+}
+
+// dayOf takes the date out of an RFC 3339 timestamp without interpreting it.
+func dayOf(stamp string) string {
+	if len(stamp) < len(dateLayout) {
+		return ""
+	}
+	day := stamp[:len(dateLayout)]
+	if _, err := time.Parse(dateLayout, day); err != nil {
+		return ""
+	}
+	return day
+}
+
+func mustDay(s string) time.Time {
+	day, _ := time.Parse(dateLayout, s)
+	return day
+}
+
+func (c *Client) get(ctx context.Context, url string, out any) error {
+	return google.Get(ctx, c.http, c.accessToken, url, out)
+}
@@ -0,0 +1,255 @@
+package gcal
+
+import (
+	"encoding/json"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+)
+
+// fakeGoogle answers the two calls this package makes, out of whatever the test
+// hands it. There is no other way to exercise this: the real Calendar needs an
+// account, a registered client and somebody's consent, and none of the three can be
+// had inside a test — so the shapes Google returns are written down here and the
+// parsing is checked against them.
+func fakeGoogle(t *testing.T, calendarList any, events map[string]any) *Client {
+	t.Helper()
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "application/json")
+		switch {
+		case strings.HasPrefix(r.URL.Path, "/users/me/calendarList"):
+			_ = json.NewEncoder(w).Encode(calendarList)
+		case strings.HasPrefix(r.URL.Path, "/calendars/"):
+			id := strings.TrimSuffix(strings.TrimPrefix(r.URL.Path, "/calendars/"), "/events")
+			body, ok := events[id]
+			if !ok {
+				http.Error(w, `{"error":"not found"}`, http.StatusNotFound)
+				return
+			}
+			_ = json.NewEncoder(w).Encode(body)
+		default:
+			http.Error(w, "unexpected path "+r.URL.Path, http.StatusNotFound)
+		}
+	}))
+	t.Cleanup(srv.Close)
+	return NewClient("token").At(srv.URL)
+}
+
+func TestCalendarsPrefersTheNameThePersonGaveIt(t *testing.T) {
+	client := fakeGoogle(t, map[string]any{
+		"items": []map[string]any{
+			{"id": "primary", "summary": "[email protected]", "backgroundColor": "#3f51b5",
+				"timeZone": "Europe/Copenhagen", "primary": true, "accessRole": "owner"},
+			{"id": "fam", "summary": "Family", "summaryOverride": "Familien",
+				"backgroundColor": "#0b8043", "accessRole": "reader"},
+			// A calendar removed from the list still arrives, flagged.
+			{"id": "gone", "summary": "Væk", "deleted": true, "accessRole": "reader"},
+		},
+	}, nil)
+
+	got, err := client.Calendars(t.Context())
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(got) != 2 {
+		t.Fatalf("got %d calendars, want 2 — a deleted one is not one you can show", len(got))
+	}
+	if got[1].Name != "Familien" {
+		t.Errorf("name = %q; summaryOverride is the name the person will look for", got[1].Name)
+	}
+	if !got[0].Primary || !got[0].Owner {
+		t.Errorf("the primary calendar came back as %+v", got[0])
+	}
+	if got[1].Owner {
+		t.Error("a reader was reported as an owner; nothing may offer to write to it")
+	}
+	if got[0].Colour != "#3f51b5" {
+		t.Errorf("colour = %q; two calendars in one grid are told apart by it", got[0].Colour)
+	}
+}
+
+// The three shapes an event arrives in, and the one shape a grid can read.
+func TestEventsBecomeDaysAGridCanAskAbout(t *testing.T) {
+	client := fakeGoogle(t, nil, map[string]any{
+		"primary": map[string]any{
+			"items": []map[string]any{
+				{
+					"id": "timed", "summary": "Bestyrelsesmøde", "htmlLink": "https://cal/1",
+					"start": map[string]string{"dateTime": "2026-08-20T14:00:00+02:00"},
+					"end":   map[string]string{"dateTime": "2026-08-20T15:30:00+02:00"},
+				},
+				{
+					// All-day, one day. Google's end is the day after.
+					"id": "allday", "summary": "Fridag",
+					"start": map[string]string{"date": "2026-08-21"},
+					"end":   map[string]string{"date": "2026-08-22"},
+				},
+				{
+					// All-day, three days.
+					"id": "trip", "summary": "Aarhus",
+					"start": map[string]string{"date": "2026-08-24"},
+					"end":   map[string]string{"date": "2026-08-27"},
+				},
+				{
+					// Runs to midnight, which is the evening before as far as a
+					// grid is concerned.
+					"id": "late", "summary": "Nattevagt",
+					"start": map[string]string{"dateTime": "2026-08-22T20:00:00+02:00"},
+					"end":   map[string]string{"dateTime": "2026-08-23T00:00:00+02:00"},
+				},
+				{
+					// A cancelled occurrence of a recurring event.
+					"id": "off", "status": "cancelled", "summary": "Aflyst",
+					"start": map[string]string{"date": "2026-08-25"},
+					"end":   map[string]string{"date": "2026-08-26"},
+				},
+				{
+					// Neither a date nor a dateTime: belongs on no day at all.
+					"id": "nowhere", "summary": "Uden tid",
+				},
+			},
+		},
+	})
+
+	got, err := client.Events(t.Context(), "primary", "2026-08-01", "2026-08-31")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	byID := map[string]Event{}
+	for _, e := range got {
+		byID[e.ID] = e
+	}
+	if len(got) != 4 {
+		t.Fatalf("got %d events, want 4: %+v", len(got), got)
+	}
+	if _, ok := byID["off"]; ok {
+		t.Error("a cancelled occurrence was kept; it is an event that is not happening")
+	}
+	if _, ok := byID["nowhere"]; ok {
+		t.Error("an event with no time was kept; there is no cell to draw it in")
+	}
+
+	timed := byID["timed"]
+	if timed.AllDay || timed.StartDay != "2026-08-20" || timed.EndDay != "2026-08-20" {
+		t.Errorf("timed = %+v", timed)
+	}
+	if timed.StartsAt != "2026-08-20T14:00:00+02:00" {
+		t.Errorf("the instant was rewritten: %q", timed.StartsAt)
+	}
+
+	allday := byID["allday"]
+	if !allday.AllDay || allday.StartDay != "2026-08-21" || allday.EndDay != "2026-08-21" {
+		t.Errorf("allday = %+v; Google's end date is exclusive and has to be corrected here",
+			allday)
+	}
+	if allday.StartsAt != "" {
+		t.Errorf("an all-day event was given an instant: %q — it has a day, not a moment",
+			allday.StartsAt)
+	}
+
+	if trip := byID["trip"]; trip.StartDay != "2026-08-24" || trip.EndDay != "2026-08-26" {
+		t.Errorf("trip = %+v, want 24th to 26th inclusive", trip)
+	}
+	if late := byID["late"]; late.EndDay != "2026-08-22" {
+		t.Errorf("late ends on %q; an event running to midnight ends the evening before, "+
+			"or every one of them puts a chip in the following day", late.EndDay)
+	}
+}
+
+// An event with no title has to say so. A blank chip in a grid reads as a
+// rendering fault rather than as an empty title.
+func TestAnEventWithNoTitleStillSaysSomething(t *testing.T) {
+	client := fakeGoogle(t, nil, map[string]any{
+		"c": map[string]any{"items": []map[string]any{{
+			"id":    "x",
+			"start": map[string]string{"date": "2026-08-20"},
+			"end":   map[string]string{"date": "2026-08-21"},
+		}}},
+	})
+	got, err := client.Events(t.Context(), "c", "2026-08-01", "2026-08-31")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(got) != 1 || got[0].Summary == "" {
+		t.Fatalf("got %+v", got)
+	}
+}
+
+// The window is asked for with a day of slack at each end, because an event late
+// in the evening in Copenhagen is the next day in UTC. The slack must not leak
+// out: an event on the day before the window is not in the window.
+func TestTheSlackAtTheEdgesIsThrownAwayAgain(t *testing.T) {
+	client := fakeGoogle(t, nil, map[string]any{
+		"c": map[string]any{"items": []map[string]any{
+			{"id": "before", "summary": "For tidligt",
+				"start": map[string]string{"date": "2026-08-09"},
+				"end":   map[string]string{"date": "2026-08-10"}},
+			{"id": "inside", "summary": "Med",
+				"start": map[string]string{"date": "2026-08-10"},
+				"end":   map[string]string{"date": "2026-08-11"}},
+			{"id": "after", "summary": "For sent",
+				"start": map[string]string{"date": "2026-08-21"},
+				"end":   map[string]string{"date": "2026-08-22"}},
+		}},
+	})
+	got, err := client.Events(t.Context(), "c", "2026-08-10", "2026-08-20")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(got) != 1 || got[0].ID != "inside" {
+		t.Fatalf("got %+v, want only the one inside the window", got)
+	}
+}
+
+// A page token has to be followed, or a busy calendar silently shows its first
+// page and nothing else — which is a calendar that lies about a day being clear.
+func TestEveryPageIsRead(t *testing.T) {
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "application/json")
+		body := map[string]any{
+			"items": []map[string]any{{"id": "a", "summary": "Første",
+				"start": map[string]string{"date": "2026-08-11"},
+				"end":   map[string]string{"date": "2026-08-12"}}},
+			"nextPageToken": "more",
+		}
+		if r.URL.Query().Get("pageToken") == "more" {
+			body = map[string]any{"items": []map[string]any{{"id": "b", "summary": "Anden",
+				"start": map[string]string{"date": "2026-08-12"},
+				"end":   map[string]string{"date": "2026-08-13"}}}}
+		}
+		_ = json.NewEncoder(w).Encode(body)
+	}))
+	defer srv.Close()
+
+	got, err := NewClient("t").At(srv.URL).Events(t.Context(), "c", "2026-08-01", "2026-08-31")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(got) != 2 {
+		t.Fatalf("got %d events, want both pages: %+v", len(got), got)
+	}
+}
+
+// A 401 is not a failure to retry; it is a connection that has ended. Telling the
+// two apart is what stops a revoked account being polled every ten minutes for ever.
+func TestARefusedTokenIsItsOwnError(t *testing.T) {
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		http.Error(w, `{"error":"invalid_credentials"}`, http.StatusUnauthorized)
+	}))
+	defer srv.Close()
+
+	_, err := NewClient("spent").At(srv.URL).Calendars(t.Context())
+	if err != ErrUnauthorized {
+		t.Fatalf("err = %v, want ErrUnauthorized", err)
+	}
+}
+
+// Read-only, and only the calendar. The consent screen is what somebody agrees to,
+// and a scope that quietly grew is a promise quietly broken.
+func TestTheScopeIsReadOnly(t *testing.T) {
+	if !strings.HasSuffix(Scope, "calendar.readonly") {
+		t.Errorf("scope = %q; nothing here writes a calendar", Scope)
+	}
+}
@@ -1,5 +1,5 @@
-// Package gmail implements the OAuth2 authorisation-code flow with PKCE against
-// Google, and the small slice of the Gmail API verdande needs.
+// Package gmail is the small slice of the Gmail API verdande needs, and the scope
+// it asks for.
 //
 // The connection is one-way on purpose: a starred or labelled message becomes a
 // task, and nothing verdande does afterwards touches the mailbox. Unstarring the
@@ -9,200 +9,51 @@
 //
 // Scope is gmail.readonly. verdande never needs to send, modify or delete, and
 // asking for less is what makes the consent screen something a person can agree to.
+//
+// The OAuth flow itself moved to internal/google when Calendar needed the same one.
+// The names below are aliases so that every call site — and this package's own
+// tests — still read as Gmail's, which is what they are: one registration, one
+// flow, one scope each.
 package gmail

 import (
 	"context"
-	"crypto/rand"
-	"crypto/sha256"
-	"encoding/base64"
-	"encoding/json"
 	"fmt"
 	"net/http"
 	"net/url"
 	"strings"
 	"time"
+
+	"github.com/kristianwind/verdande/internal/google"
 )

-const (
-	authEndpoint         = "https://accounts.google.com/o/oauth2/v2/auth"
-	defaultTokenEndpoint = "https://oauth2.googleapis.com/token"
-	defaultAPIBase       = "https://gmail.googleapis.com/gmail/v1"
+// Read-only, and only mail. Not profile, not contacts, not send.
+const Scope = "https://www.googleapis.com/auth/gmail.readonly"

-	// Read-only, and only mail. Not profile, not contacts, not send.
-	Scope = "https://www.googleapis.com/auth/gmail.readonly"
+const defaultAPIBase = "https://gmail.googleapis.com/gmail/v1"
+
+// The OAuth flow, which is Google's rather than Gmail's.
+type (
+	Config = google.Config
+	PKCE   = google.PKCE
+	Token  = google.Token
 )

-// Endpoints is where Google is.
-//
-// A field rather than a constant so a test can point it at a server it controls.
-// There is no other way to exercise what happens when Gmail is slow or refuses —
-// and "the sync comes back before whatever sits in front of this server gives up
-// on it" is exactly the kind of promise worth a test and impossible to make
-// against the real thing.
-//
-// The zero value is Google, so nothing outside a test has to know it exists.
-type Endpoints struct {
-	Token string
-	API   string
-}
-
-func (e Endpoints) token() string {
-	if e.Token != "" {
-		return e.Token
-	}
-	return defaultTokenEndpoint
-}
-
-func (e Endpoints) api() string {
-	if e.API != "" {
-		return e.API
-	}
-	return defaultAPIBase
-}
-
-// Config is the OAuth client the operator registered in Google Cloud. It belongs to
-// the instance rather than to a person: one registration, any number of users.
-type Config struct {
-	ClientID     string
-	ClientSecret string
-	RedirectURL  string
-	// Endpoints is Google unless a test says otherwise.
-	Endpoints Endpoints
-}
-
-func (c Config) Configured() bool {
-	return c.ClientID != "" && c.ClientSecret != "" && c.RedirectURL != ""
-}
-
-// PKCE is the proof-key pair for one authorisation attempt.
-//
-// PKCE on a server-side client is not strictly required — the client secret already
-// authenticates the token exchange — but it costs nothing and closes the window in
-// which an authorisation code intercepted from the redirect could be replayed
-// before verdande gets to it.
-type PKCE struct {
-	Verifier  string
-	Challenge string
-	State     string
-}
-
-func NewPKCE() (PKCE, error) {
-	verifier, err := randomString(64)
-	if err != nil {
-		return PKCE{}, err
-	}
-	state, err := randomString(32)
-	if err != nil {
-		return PKCE{}, err
-	}
-	sum := sha256.Sum256([]byte(verifier))
-	return PKCE{
-		Verifier:  verifier,
-		Challenge: base64.RawURLEncoding.EncodeToString(sum[:]),
-		State:     state,
-	}, nil
-}
-
-// AuthURL is where the browser is sent to ask the person for consent.
-func (c Config) AuthURL(p PKCE) string {
-	v := url.Values{}
-	v.Set("client_id", c.ClientID)
-	v.Set("redirect_uri", c.RedirectURL)
-	v.Set("response_type", "code")
-	v.Set("scope", Scope)
-	v.Set("state", p.State)
-	v.Set("code_challenge", p.Challenge)
-	v.Set("code_challenge_method", "S256")
-	// Without both of these Google returns no refresh token on a re-authorisation,
-	// and the connection silently stops working an hour later.
-	v.Set("access_type", "offline")
-	v.Set("prompt", "consent")
-	return authEndpoint + "?" + v.Encode()
-}
-
-type Token struct {
-	AccessToken  string
-	RefreshToken string
-	ExpiresAt    time.Time
-}
-
-// Exchange trades the authorisation code for tokens.
-func (c Config) Exchange(ctx context.Context, code string, p PKCE) (Token, error) {
-	form := url.Values{}
-	form.Set("code", code)
-	form.Set("client_id", c.ClientID)
-	form.Set("client_secret", c.ClientSecret)
-	form.Set("redirect_uri", c.RedirectURL)
-	form.Set("grant_type", "authorization_code")
-	form.Set("code_verifier", p.Verifier)
-
-	return c.token(ctx, form)
-}
-
-// Refresh gets a fresh access token. Google does not return a new refresh token
-// here, so the caller keeps the one it has.
-func (c Config) Refresh(ctx context.Context, refreshToken string) (Token, error) {
-	form := url.Values{}
-	form.Set("refresh_token", refreshToken)
-	form.Set("client_id", c.ClientID)
-	form.Set("client_secret", c.ClientSecret)
-	form.Set("grant_type", "refresh_token")
-
-	token, err := c.token(ctx, form)
-	if err != nil {
-		return Token{}, err
-	}
-	token.RefreshToken = refreshToken
-	return token, nil
-}
-
-func (c Config) token(ctx context.Context, form url.Values) (Token, error) {
-	req, err := http.NewRequestWithContext(ctx, http.MethodPost, c.Endpoints.token(),
-		strings.NewReader(form.Encode()))
-	if err != nil {
-		return Token{}, err
-	}
-	req.Header.Set("Content-Type", "application/x-www-form-urlencoded")
-
-	resp, err := (&http.Client{Timeout: 30 * time.Second}).Do(req)
-	if err != nil {
-		return Token{}, err
-	}
-	defer resp.Body.Close()
-
-	var parsed struct {
-		AccessToken      string `json:"access_token"`
-		RefreshToken     string `json:"refresh_token"`
-		ExpiresIn        int    `json:"expires_in"`
-		Error            string `json:"error"`
-		ErrorDescription string `json:"error_description"`
-	}
-	if err := json.NewDecoder(resp.Body).Decode(&parsed); err != nil {
-		return Token{}, fmt.Errorf("gmail: reading token response: %w", err)
-	}
-	if parsed.Error != "" {
-		return Token{}, fmt.Errorf("gmail: %s: %s", parsed.Error, parsed.ErrorDescription)
-	}
-	if resp.StatusCode != http.StatusOK || parsed.AccessToken == "" {
-		return Token{}, fmt.Errorf("gmail: token exchange failed with %s", resp.Status)
-	}
-
-	return Token{
-		AccessToken:  parsed.AccessToken,
-		RefreshToken: parsed.RefreshToken,
-		// A minute of slack, so a token that is about to expire is refreshed
-		// rather than used and rejected.
-		ExpiresAt: time.Now().Add(time.Duration(parsed.ExpiresIn-60) * time.Second),
-	}, nil
-}
+var (
+	NewPKCE         = google.NewPKCE
+	ErrUnauthorized = google.ErrUnauthorized
+)

 // --- the API ---------------------------------------------------------------------

 type Client struct {
 	accessToken string
-	endpoints   Endpoints
-	http        *http.Client
+	// base is where the Gmail API is. A field rather than a constant so a test can
+	// point it at a server it controls — and "the sync comes back before whatever
+	// sits in front of this server gives up on it" is exactly the kind of promise
+	// worth a test and impossible to make against the real thing. Empty is Google.
+	base string
+	http *http.Client
 }

 func NewClient(accessToken string) *Client {
@@ -210,11 +61,18 @@ func NewClient(accessToken string) *Client {
 }

 // At points the client at another server. Tests only; the zero value is Google.
-func (c *Client) At(e Endpoints) *Client {
-	c.endpoints = e
+func (c *Client) At(base string) *Client {
+	c.base = base
 	return c
 }

+func (c *Client) api() string {
+	if c.base != "" {
+		return c.base
+	}
+	return defaultAPIBase
+}
+
 // Message is the part of a Gmail message a task is made from.
 type Message struct {
 	ID       string
@@ -233,7 +91,7 @@ func (c *Client) Profile(ctx context.Context) (string, error) {
 	var parsed struct {
 		EmailAddress string `json:"emailAddress"`
 	}
-	if err := c.get(ctx, c.endpoints.api()+"/users/me/profile", &parsed); err != nil {
+	if err := c.get(ctx, c.api()+"/users/me/profile", &parsed); err != nil {
 		return "", err
 	}
 	return parsed.EmailAddress, nil
@@ -257,7 +115,7 @@ func (c *Client) List(ctx context.Context, query string, max int) ([]string, err
 			ID string `json:"id"`
 		} `json:"messages"`
 	}
-	if err := c.get(ctx, c.endpoints.api()+"/users/me/messages?"+v.Encode(), &parsed); err != nil {
+	if err := c.get(ctx, c.api()+"/users/me/messages?"+v.Encode(), &parsed); err != nil {
 		return nil, err
 	}

@@ -288,7 +146,7 @@ func (c *Client) Get(ctx context.Context, id string) (Message, error) {
 			} `json:"headers"`
 		} `json:"payload"`
 	}
-	if err := c.get(ctx, c.endpoints.api()+"/users/me/messages/"+url.PathEscape(id)+"?"+v.Encode(), &parsed); err != nil {
+	if err := c.get(ctx, c.api()+"/users/me/messages/"+url.PathEscape(id)+"?"+v.Encode(), &parsed); err != nil {
 		return Message{}, err
 	}

@@ -308,31 +166,9 @@ func (c *Client) Get(ctx context.Context, id string) (Message, error) {
 }

 func (c *Client) get(ctx context.Context, url string, out any) error {
-	req, err := http.NewRequestWithContext(ctx, http.MethodGet, url, nil)
-	if err != nil {
-		return err
-	}
-	req.Header.Set("Authorization", "Bearer "+c.accessToken)
-
-	resp, err := c.http.Do(req)
-	if err != nil {
-		return err
-	}
-	defer resp.Body.Close()
-
-	if resp.StatusCode == http.StatusUnauthorized {
-		return ErrUnauthorized
-	}
-	if resp.StatusCode != http.StatusOK {
-		return fmt.Errorf("gmail: %s", resp.Status)
-	}
-	return json.NewDecoder(resp.Body).Decode(out)
+	return google.Get(ctx, c.http, c.accessToken, url, out)
 }

-// ErrUnauthorized means the tokens are no longer good — the person revoked access,
-// or changed their password. The caller disconnects rather than retrying.
-var ErrUnauthorized = fmt.Errorf("gmail: authorisation was refused")
-
 // SenderName pulls "Anders Jensen" out of "Anders Jensen <[email protected]>",
 // falling back to the address when there is no display name.
 func SenderName(from string) string {
@@ -375,11 +211,3 @@ func Query(trigger, label string) string {
 	terms = append(terms, "newer_than:30d")
 	return strings.Join(terms, " ")
 }
-
-func randomString(n int) (string, error) {
-	b := make([]byte, n)
-	if _, err := rand.Read(b); err != nil {
-		return "", err
-	}
-	return base64.RawURLEncoding.EncodeToString(b)[:n], nil
-}
@@ -1,113 +1,19 @@
 package gmail

 import (
-	"crypto/sha256"
-	"encoding/base64"
-	"net/url"
 	"strings"
 	"testing"
 )

-// The challenge has to be the SHA-256 of the verifier, base64url without padding.
-// Getting this wrong means Google refuses every exchange with a message that does
-// not say which end is at fault.
-func TestPKCEChallengeMatchesItsVerifier(t *testing.T) {
-	p, err := NewPKCE()
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	sum := sha256.Sum256([]byte(p.Verifier))
-	want := base64.RawURLEncoding.EncodeToString(sum[:])
-	if p.Challenge != want {
-		t.Errorf("challenge = %q, want %q", p.Challenge, want)
-	}
-
-	// RFC 7636 requires 43–128 characters, and no padding.
-	if n := len(p.Verifier); n < 43 || n > 128 {
-		t.Errorf("verifier is %d characters, outside the 43–128 the spec allows", n)
-	}
-	if strings.ContainsAny(p.Verifier, "=+/") {
-		t.Errorf("verifier %q contains characters that are not URL-safe", p.Verifier)
-	}
-	if p.State == "" {
-		t.Error("no state was generated")
-	}
-
-	// Two attempts must not share anything.
-	other, err := NewPKCE()
-	if err != nil {
-		t.Fatal(err)
-	}
-	if other.Verifier == p.Verifier || other.State == p.State {
-		t.Error("two authorisation attempts produced the same secrets")
-	}
-}
-
-func TestAuthURL(t *testing.T) {
-	cfg := Config{
-		ClientID:     "client-123",
-		ClientSecret: "secret",
-		RedirectURL:  "https://todo.example.dk/oauth/gmail/callback",
-	}
-	p, err := NewPKCE()
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	raw := cfg.AuthURL(p)
-	parsed, err := url.Parse(raw)
-	if err != nil {
-		t.Fatalf("the URL does not parse: %v", err)
-	}
-	q := parsed.Query()
-
-	checks := map[string]string{
-		"client_id":             cfg.ClientID,
-		"redirect_uri":          cfg.RedirectURL,
-		"response_type":         "code",
-		"scope":                 Scope,
-		"code_challenge":        p.Challenge,
-		"code_challenge_method": "S256",
-		"state":                 p.State,
-		// Without both of these Google returns no refresh token on a
-		// re-authorisation, and the connection dies silently an hour later.
-		"access_type": "offline",
-		"prompt":      "consent",
-	}
-	for key, want := range checks {
-		if got := q.Get(key); got != want {
-			t.Errorf("%s = %q, want %q", key, got, want)
-		}
-	}
-
-	// The verifier itself must never leave the server.
-	if strings.Contains(raw, p.Verifier) {
-		t.Error("the code verifier was put in the authorisation URL")
-	}
-	// Read-only, and only mail.
+// The scope is the one thing verdande chooses about the connection, and it is the
+// one the person reads on the consent screen. The flow itself is exercised in
+// internal/google; what belongs here is that Gmail still asks for read-only mail.
+func TestTheScopeIsReadOnlyMail(t *testing.T) {
 	if !strings.HasSuffix(Scope, "gmail.readonly") {
 		t.Errorf("scope = %q; verdande never needs to send or modify", Scope)
 	}
 }

-func TestConfigured(t *testing.T) {
-	full := Config{ClientID: "a", ClientSecret: "b", RedirectURL: "c"}
-	if !full.Configured() {
-		t.Error("a complete config is not reported as configured")
-	}
-	for _, partial := range []Config{
-		{},
-		{ClientID: "a"},
-		{ClientID: "a", ClientSecret: "b"},
-		{ClientSecret: "b", RedirectURL: "c"},
-	} {
-		if partial.Configured() {
-			t.Errorf("%+v was reported as configured", partial)
-		}
-	}
-}
-
 func TestQuery(t *testing.T) {
 	cases := []struct {
 		trigger, label string
@@ -0,0 +1,224 @@
+// Package google implements the OAuth2 authorisation-code flow with PKCE against
+// Google.
+//
+// It was written inside internal/gmail, because Gmail was the only thing that
+// needed it. Calendar needs the same flow — the same endpoints, the same PKCE, the
+// same refresh — and the only thing that differs between them is one string: the
+// scope. A second copy would be a second place for "access_type=offline" to be
+// forgotten, which is the mistake that makes a connection die silently an hour
+// after it was made.
+//
+// What is *not* here is the API calls. Those differ completely, so gmail and gcal
+// keep their own clients and share only the way in.
+package google
+
+import (
+	"context"
+	"crypto/rand"
+	"crypto/sha256"
+	"encoding/base64"
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"net/url"
+	"strings"
+	"time"
+)
+
+const (
+	authEndpoint         = "https://accounts.google.com/o/oauth2/v2/auth"
+	defaultTokenEndpoint = "https://oauth2.googleapis.com/token"
+)
+
+// Config is the OAuth client the operator registered in Google Cloud, plus the
+// scope one feature is asking for.
+//
+// The client belongs to the instance rather than to a person: one registration,
+// any number of users. The scope belongs to the feature: Gmail and Calendar sign
+// in through the same registration and ask for different things, and Google issues
+// a refresh token per authorisation — so connecting one does not disturb the other.
+type Config struct {
+	ClientID     string
+	ClientSecret string
+	RedirectURL  string
+	Scope        string
+
+	// TokenURL is where Google is. A field rather than a constant so a test can
+	// point it at a server it controls: there is no other way to exercise what
+	// happens when the token endpoint is slow or refuses. Empty is Google, so
+	// nothing outside a test has to know it exists.
+	TokenURL string
+}
+
+func (c Config) Configured() bool {
+	return c.ClientID != "" && c.ClientSecret != "" && c.RedirectURL != ""
+}
+
+func (c Config) tokenURL() string {
+	if c.TokenURL != "" {
+		return c.TokenURL
+	}
+	return defaultTokenEndpoint
+}
+
+// PKCE is the proof-key pair for one authorisation attempt.
+//
+// PKCE on a server-side client is not strictly required — the client secret already
+// authenticates the token exchange — but it costs nothing and closes the window in
+// which an authorisation code intercepted from the redirect could be replayed
+// before verdande gets to it.
+type PKCE struct {
+	Verifier  string
+	Challenge string
+	State     string
+}
+
+func NewPKCE() (PKCE, error) {
+	verifier, err := randomString(64)
+	if err != nil {
+		return PKCE{}, err
+	}
+	state, err := randomString(32)
+	if err != nil {
+		return PKCE{}, err
+	}
+	sum := sha256.Sum256([]byte(verifier))
+	return PKCE{
+		Verifier:  verifier,
+		Challenge: base64.RawURLEncoding.EncodeToString(sum[:]),
+		State:     state,
+	}, nil
+}
+
+// AuthURL is where the browser is sent to ask the person for consent.
+func (c Config) AuthURL(p PKCE) string {
+	v := url.Values{}
+	v.Set("client_id", c.ClientID)
+	v.Set("redirect_uri", c.RedirectURL)
+	v.Set("response_type", "code")
+	v.Set("scope", c.Scope)
+	v.Set("state", p.State)
+	v.Set("code_challenge", p.Challenge)
+	v.Set("code_challenge_method", "S256")
+	// Without both of these Google returns no refresh token on a re-authorisation,
+	// and the connection silently stops working an hour later.
+	v.Set("access_type", "offline")
+	v.Set("prompt", "consent")
+	return authEndpoint + "?" + v.Encode()
+}
+
+type Token struct {
+	AccessToken  string
+	RefreshToken string
+	ExpiresAt    time.Time
+}
+
+// Exchange trades the authorisation code for tokens.
+func (c Config) Exchange(ctx context.Context, code string, p PKCE) (Token, error) {
+	form := url.Values{}
+	form.Set("code", code)
+	form.Set("client_id", c.ClientID)
+	form.Set("client_secret", c.ClientSecret)
+	form.Set("redirect_uri", c.RedirectURL)
+	form.Set("grant_type", "authorization_code")
+	form.Set("code_verifier", p.Verifier)
+
+	return c.token(ctx, form)
+}
+
+// Refresh gets a fresh access token. Google does not return a new refresh token
+// here, so the caller keeps the one it has.
+func (c Config) Refresh(ctx context.Context, refreshToken string) (Token, error) {
+	form := url.Values{}
+	form.Set("refresh_token", refreshToken)
+	form.Set("client_id", c.ClientID)
+	form.Set("client_secret", c.ClientSecret)
+	form.Set("grant_type", "refresh_token")
+
+	token, err := c.token(ctx, form)
+	if err != nil {
+		return Token{}, err
+	}
+	token.RefreshToken = refreshToken
+	return token, nil
+}
+
+func (c Config) token(ctx context.Context, form url.Values) (Token, error) {
+	req, err := http.NewRequestWithContext(ctx, http.MethodPost, c.tokenURL(),
+		strings.NewReader(form.Encode()))
+	if err != nil {
+		return Token{}, err
+	}
+	req.Header.Set("Content-Type", "application/x-www-form-urlencoded")
+
+	resp, err := (&http.Client{Timeout: 30 * time.Second}).Do(req)
+	if err != nil {
+		return Token{}, err
+	}
+	defer resp.Body.Close()
+
+	var parsed struct {
+		AccessToken      string `json:"access_token"`
+		RefreshToken     string `json:"refresh_token"`
+		ExpiresIn        int    `json:"expires_in"`
+		Error            string `json:"error"`
+		ErrorDescription string `json:"error_description"`
+	}
+	if err := json.NewDecoder(resp.Body).Decode(&parsed); err != nil {
+		return Token{}, fmt.Errorf("google: reading token response: %w", err)
+	}
+	if parsed.Error != "" {
+		return Token{}, fmt.Errorf("google: %s: %s", parsed.Error, parsed.ErrorDescription)
+	}
+	if resp.StatusCode != http.StatusOK || parsed.AccessToken == "" {
+		return Token{}, fmt.Errorf("google: token exchange failed with %s", resp.Status)
+	}
+
+	return Token{
+		AccessToken:  parsed.AccessToken,
+		RefreshToken: parsed.RefreshToken,
+		// A minute of slack, so a token that is about to expire is refreshed
+		// rather than used and rejected.
+		ExpiresAt: time.Now().Add(time.Duration(parsed.ExpiresIn-60) * time.Second),
+	}, nil
+}
+
+// ErrUnauthorized means the tokens are no longer good — the person revoked access,
+// or changed their password. The caller disconnects rather than retrying.
+var ErrUnauthorized = fmt.Errorf("google: authorisation was refused")
+
+// Get performs an authorised GET and decodes the JSON body into out.
+//
+// Shared by the two API clients because the interesting part is the same in both:
+// a 401 is not a failure to retry, it is a connection that has ended, and telling
+// those apart is what stops a revoked account being polled every ten minutes for
+// ever.
+func Get(ctx context.Context, client *http.Client, accessToken, url string, out any) error {
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, url, nil)
+	if err != nil {
+		return err
+	}
+	req.Header.Set("Authorization", "Bearer "+accessToken)
+
+	resp, err := client.Do(req)
+	if err != nil {
+		return err
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode == http.StatusUnauthorized {
+		return ErrUnauthorized
+	}
+	if resp.StatusCode != http.StatusOK {
+		return fmt.Errorf("google: %s", resp.Status)
+	}
+	return json.NewDecoder(resp.Body).Decode(out)
+}
+
+func randomString(n int) (string, error) {
+	b := make([]byte, n)
+	if _, err := rand.Read(b); err != nil {
+		return "", err
+	}
+	return base64.RawURLEncoding.EncodeToString(b)[:n], nil
+}
@@ -0,0 +1,127 @@
+package google
+
+import (
+	"crypto/sha256"
+	"encoding/base64"
+	"net/url"
+	"strings"
+	"testing"
+)
+
+// The challenge has to be the SHA-256 of the verifier, base64url without padding.
+// Getting this wrong means Google refuses every exchange with a message that does
+// not say which end is at fault.
+func TestPKCEChallengeMatchesItsVerifier(t *testing.T) {
+	p, err := NewPKCE()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	sum := sha256.Sum256([]byte(p.Verifier))
+	want := base64.RawURLEncoding.EncodeToString(sum[:])
+	if p.Challenge != want {
+		t.Errorf("challenge = %q, want %q", p.Challenge, want)
+	}
+
+	// RFC 7636 requires 43–128 characters, and no padding.
+	if n := len(p.Verifier); n < 43 || n > 128 {
+		t.Errorf("verifier is %d characters, outside the 43–128 the spec allows", n)
+	}
+	if strings.ContainsAny(p.Verifier, "=+/") {
+		t.Errorf("verifier %q contains characters that are not URL-safe", p.Verifier)
+	}
+	if p.State == "" {
+		t.Error("no state was generated")
+	}
+
+	// Two attempts must not share anything.
+	other, err := NewPKCE()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if other.Verifier == p.Verifier || other.State == p.State {
+		t.Error("two authorisation attempts produced the same secrets")
+	}
+}
+
+func TestAuthURL(t *testing.T) {
+	cfg := Config{
+		ClientID:     "client-123",
+		ClientSecret: "secret",
+		RedirectURL:  "https://todo.example.dk/oauth/gmail/callback",
+		Scope:        "https://www.googleapis.com/auth/gmail.readonly",
+	}
+	p, err := NewPKCE()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	raw := cfg.AuthURL(p)
+	parsed, err := url.Parse(raw)
+	if err != nil {
+		t.Fatalf("the URL does not parse: %v", err)
+	}
+	q := parsed.Query()
+
+	checks := map[string]string{
+		"client_id":             cfg.ClientID,
+		"redirect_uri":          cfg.RedirectURL,
+		"response_type":         "code",
+		"scope":                 cfg.Scope,
+		"code_challenge":        p.Challenge,
+		"code_challenge_method": "S256",
+		"state":                 p.State,
+		// Without both of these Google returns no refresh token on a
+		// re-authorisation, and the connection dies silently an hour later.
+		"access_type": "offline",
+		"prompt":      "consent",
+	}
+	for key, want := range checks {
+		if got := q.Get(key); got != want {
+			t.Errorf("%s = %q, want %q", key, got, want)
+		}
+	}
+
+	// The verifier itself must never leave the server.
+	if strings.Contains(raw, p.Verifier) {
+		t.Error("the code verifier was put in the authorisation URL")
+	}
+}
+
+// The scope is the one thing that differs between the two features signing in
+// through this, so it has to come out of the config rather than out of a constant
+// somebody could forget to change.
+func TestTheScopeComesFromTheConfig(t *testing.T) {
+	p, err := NewPKCE()
+	if err != nil {
+		t.Fatal(err)
+	}
+	calendar := "https://www.googleapis.com/auth/calendar.readonly"
+	raw := Config{ClientID: "a", Scope: calendar}.AuthURL(p)
+
+	parsed, err := url.Parse(raw)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if got := parsed.Query().Get("scope"); got != calendar {
+		t.Errorf("scope = %q, want %q — asking for the wrong one is a consent screen "+
+			"that grants the wrong thing", got, calendar)
+	}
+}
+
+func TestConfigured(t *testing.T) {
+	full := Config{ClientID: "a", ClientSecret: "b", RedirectURL: "c"}
+	if !full.Configured() {
+		t.Error("a complete config is not reported as configured")
+	}
+	for _, partial := range []Config{
+		{},
+		{ClientID: "a"},
+		{ClientID: "a", ClientSecret: "b"},
+		{ClientSecret: "b", RedirectURL: "c"},
+	} {
+		if partial.Configured() {
+			t.Errorf("%+v was reported as configured", partial)
+		}
+	}
+}
@@ -0,0 +1,548 @@
+package httpapi
+
+import (
+	"context"
+	"errors"
+	"net/http"
+	"time"
+
+	"github.com/kristianwind/verdande/internal/gcal"
+	"github.com/kristianwind/verdande/internal/store"
+)
+
+// defaultCalendarSyncBudget bounds one "fetch now" when nothing else says
+// otherwise. Well under the hundred seconds a proxy is willing to wait, so this
+// server is the one that answers a slow Google rather than Cloudflare's own HTML
+// page — which is how a failure arrives with no code, no message and nothing in
+// the error log.
+const defaultCalendarSyncBudget = 25 * time.Second
+
+// The window verdande keeps a copy of.
+//
+// A month grid pages, so asking Google on every arrow press would mean a round trip
+// for a question answered ninety seconds ago — a calendar slower than the calendar
+// it is showing. A cached window is the alternative, and a window has to end
+// somewhere. Ninety days back is roughly "when was that", a year forward is past
+// anything anybody has booked; between them they cover every screen the grid can
+// reach without a person noticing an edge.
+//
+// The edge is still real, and the events endpoint says where it is rather than
+// answering an empty list for a month outside it. A calendar that quietly shows no
+// events is a calendar that lies about a day being clear.
+const (
+	calendarWindowBack   = 90
+	calendarWindowAhead  = 365
+	calendarDateLayout   = "2006-01-02"
+	calendarProviderName = "google"
+)
+
+func (s *Server) calendarClient(accessToken string) *gcal.Client {
+	return gcal.NewClient(accessToken).At(s.cfg.CalendarAPIURL)
+}
+
+// calendarConfig is the same registration Gmail signs in through, asking for a
+// different scope and coming back to a different URI.
+//
+// One OAuth client, two features. Google issues a refresh token per authorisation
+// and keeps up to a hundred of them live per account, each carrying the scopes it
+// was granted with — so connecting the calendar does not disturb a working Gmail,
+// and disconnecting one does not take the other with it.
+func (s *Server) calendarConfig(ctx context.Context) gcal.Config {
+	cfg := s.gmailConfig(ctx)
+	cfg.Scope = gcal.Scope
+	cfg.RedirectURL = s.cfg.CalendarRedirectURL()
+	return cfg
+}
+
+// --- connecting ------------------------------------------------------------------
+
+// handleCalendarAuthorize starts the flow. Same shape as Gmail's, and the same
+// reason for keeping the verifier server-side: the callback arrives as a top-level
+// navigation from Google, and a SameSite=Lax cookie is the kind of thing that works
+// until a browser tightens its defaults.
+func (s *Server) handleCalendarAuthorize(w http.ResponseWriter, r *http.Request) {
+	user := userFrom(r.Context())
+	cfg := s.calendarConfig(r.Context())
+
+	if !cfg.Configured() {
+		writeError(w, http.StatusConflict, CodeGmailNotConfigured,
+			"no Google OAuth client is registered on this server")
+		return
+	}
+
+	pkce, err := gcal.NewPKCE()
+	if err != nil {
+		s.internal(w, r, "calendar pkce", err)
+		return
+	}
+
+	// Its own settings scope, not Gmail's. Two handshakes in one row would mean a
+	// person who started both flows had one verifier, and whichever came back
+	// second would be refused for a reason nothing on the screen could explain.
+	settings, err := s.db.UserSettings(r.Context(), user.ID, "calendar")
+	if err != nil {
+		s.internal(w, r, "calendar settings", err)
+		return
+	}
+	settings["pkce_verifier"] = pkce.Verifier
+	settings["pkce_state"] = pkce.State
+	// The attempt expires: a stored verifier that lives forever is a replay window
+	// that lives forever.
+	settings["pkce_expires"] = time.Now().Add(10 * time.Minute).Unix()
+
+	if err := s.db.SetUserSettings(r.Context(), user.ID, "calendar", settings); err != nil {
+		s.internal(w, r, "calendar settings", err)
+		return
+	}
+	writeJSON(w, http.StatusOK, map[string]string{"url": cfg.AuthURL(pkce)})
+}
+
+// handleCalendarCallback is where Google sends the browser back.
+//
+// It answers with a redirect into the app rather than with JSON: the person is
+// looking at a browser tab, not at a fetch response.
+func (s *Server) handleCalendarCallback(w http.ResponseWriter, r *http.Request) {
+	user := userFrom(r.Context())
+	settingsURL := s.cfg.BaseURL + "/indstillinger/integrationer"
+
+	if errParam := r.URL.Query().Get("error"); errParam != "" {
+		// Somebody clicked "cancel" on the consent screen — or, on an Internal
+		// OAuth app, Google refused an account outside the organisation with
+		// `org_internal`. Both arrive here, and the page names what it was given.
+		http.Redirect(w, r, settingsURL+"?calendar="+errParam, http.StatusFound)
+		return
+	}
+
+	code := r.URL.Query().Get("code")
+	state := r.URL.Query().Get("state")
+	if code == "" || state == "" {
+		http.Redirect(w, r, settingsURL+"?calendar=invalid", http.StatusFound)
+		return
+	}
+
+	settings, err := s.db.UserSettings(r.Context(), user.ID, "calendar")
+	if err != nil {
+		s.internal(w, r, "calendar settings", err)
+		return
+	}
+	verifier, _ := settings["pkce_verifier"].(string)
+	expected, _ := settings["pkce_state"].(string)
+	expires, _ := settings["pkce_expires"].(float64)
+
+	// The state has to match, or this endpoint accepts a code from anywhere.
+	if verifier == "" || expected == "" || state != expected {
+		http.Redirect(w, r, settingsURL+"?calendar=state", http.StatusFound)
+		return
+	}
+	if int64(expires) < time.Now().Unix() {
+		http.Redirect(w, r, settingsURL+"?calendar=expired", http.StatusFound)
+		return
+	}
+
+	token, err := s.calendarConfig(r.Context()).Exchange(r.Context(), code,
+		gcal.PKCE{Verifier: verifier})
+	if err != nil {
+		s.log.Error("calendar exchange", "err", err, "user", user.ID)
+		http.Redirect(w, r, settingsURL+"?calendar=failed", http.StatusFound)
+		return
+	}
+	if token.RefreshToken == "" {
+		// Without one the connection dies in an hour. Google only withholds it when
+		// the consent prompt was skipped, which access_type and prompt are meant to
+		// prevent — so this means something is wrong with the client registration
+		// rather than with this request.
+		s.log.Error("calendar returned no refresh token", "user", user.ID)
+		http.Redirect(w, r, settingsURL+"?calendar=norefresh", http.StatusFound)
+		return
+	}
+
+	// The one-time values are cleared: keeping a spent verifier serves nothing and
+	// is one more secret at rest.
+	delete(settings, "pkce_verifier")
+	delete(settings, "pkce_state")
+	delete(settings, "pkce_expires")
+	if err := s.db.SetUserSettings(r.Context(), user.ID, "calendar", settings); err != nil {
+		s.internal(w, r, "clear calendar handshake", err)
+		return
+	}
+
+	account := &store.CalendarAccount{
+		UserID: user.ID, Provider: calendarProviderName,
+		RefreshToken: token.RefreshToken, AccessToken: token.AccessToken,
+		ExpiresAt: token.ExpiresAt,
+	}
+	if err := s.db.SaveCalendarAccount(r.Context(), account); err != nil {
+		s.internal(w, r, "save calendar tokens", err)
+		return
+	}
+
+	// The list of calendars, fetched now so the page that opens next has something
+	// to tick rather than an empty panel and a button. Best effort: an account that
+	// connects but cannot list itself is still connected, and the status endpoint
+	// asks again when it finds nothing.
+	if _, err := s.refreshCalendarList(r.Context(), account); err != nil {
+		s.log.Warn("calendar list", "err", err, "user", user.ID)
+	}
+
+	s.log.Info("calendar connected", "user", user.ID, "account", account.Account)
+	http.Redirect(w, r, settingsURL+"?calendar=connected", http.StatusFound)
+}
+
+// --- what the settings page reads --------------------------------------------------
+
+type calendarStatusJSON struct {
+	Connected bool             `json:"connected"`
+	Account   string           `json:"account,omitempty"`
+	Calendars []store.Calendar `json:"calendars"`
+	// RedirectURI is what has to be registered with Google, spelled out. Derived
+	// from VERDANDE_BASE_URL and matched exactly — the single most likely thing to
+	// be wrong, and the error Google gives for it names neither value.
+	RedirectURI string `json:"redirect_uri"`
+	// HasClient says whether there is an OAuth registration to connect through at
+	// all, so the page can explain rather than offer a button that answers 409.
+	HasClient  bool   `json:"has_client"`
+	LastSyncAt string `json:"last_sync_at,omitempty"`
+	// ReadOnly is stated rather than assumed. Nothing writes a Google calendar, and
+	// an interface that quietly looks editable is one somebody will try to edit.
+	ReadOnly bool `json:"read_only"`
+}
+
+func (s *Server) handleGetCalendar(w http.ResponseWriter, r *http.Request) {
+	user := userFrom(r.Context())
+
+	out := calendarStatusJSON{
+		Calendars:   []store.Calendar{},
+		RedirectURI: s.cfg.CalendarRedirectURL(),
+		HasClient:   s.calendarConfig(r.Context()).Configured(),
+		ReadOnly:    true,
+	}
+
+	account, err := s.db.CalendarAccountFor(r.Context(), user.ID, calendarProviderName)
+	if err != nil {
+		s.internal(w, r, "calendar account", err)
+		return
+	}
+	if account == nil || account.RefreshToken == "" {
+		writeJSON(w, http.StatusOK, out)
+		return
+	}
+
+	out.Connected = true
+	out.Account = account.Account
+	if !account.LastSyncAt.IsZero() {
+		out.LastSyncAt = account.LastSyncAt.Format(time.RFC3339)
+	}
+
+	calendars, err := s.db.Calendars(r.Context(), account.ID)
+	if err != nil {
+		s.internal(w, r, "calendars", err)
+		return
+	}
+	// An account connected during a Google hiccup has no calendars and no way back:
+	// the person sees an empty list and nothing to press. Asking again here costs
+	// one request on a page nobody opens often, and means the wrong answer lasts
+	// until the next look rather than for ever. Same reasoning as the Gmail address.
+	if len(calendars) == 0 {
+		if fetched, err := s.refreshCalendarList(r.Context(), account); err == nil {
+			calendars = fetched
+			out.Account = account.Account
+		} else {
+			s.log.Warn("calendar list", "err", err, "user", user.ID)
+		}
+	}
+	if calendars != nil {
+		out.Calendars = calendars
+	}
+	writeJSON(w, http.StatusOK, out)
+}
+
+type showCalendarsRequest struct {
+	// Shown is the whole set, not one flip. Same reasoning as the projects' order:
+	// a person has a handful of calendars, the question is "these ones", and a list
+	// that can only be built by several requests can land half applied.
+	Shown []string `json:"shown"`
+}
+
+func (s *Server) handleSetCalendars(w http.ResponseWriter, r *http.Request) {
+	var req showCalendarsRequest
+	if err := decodeJSON(w, r, &req); err != nil {
+		return
+	}
+	user := userFrom(r.Context())
+
+	account, err := s.db.CalendarAccountFor(r.Context(), user.ID, calendarProviderName)
+	if err != nil {
+		s.internal(w, r, "calendar account", err)
+		return
+	}
+	if account == nil {
+		// A 404 rather than a 409: everything the caller may not see answers 404,
+		// and "there is no such connection" is the true answer either way.
+		writeError(w, http.StatusNotFound, CodeNotFound, "no calendar is connected")
+		return
+	}
+	if err := s.db.ShowCalendars(r.Context(), account.ID, req.Shown); err != nil {
+		s.internal(w, r, "show calendars", err)
+		return
+	}
+	w.WriteHeader(http.StatusNoContent)
+}
+
+// handleDisconnectCalendar forgets the connection, and the copy of the calendars
+// with it. Unlike the tasks a mailbox made, none of this is the person's own work.
+func (s *Server) handleDisconnectCalendar(w http.ResponseWriter, r *http.Request) {
+	user := userFrom(r.Context())
+	account, err := s.db.CalendarAccountFor(r.Context(), user.ID, calendarProviderName)
+	if err != nil {
+		s.internal(w, r, "calendar account", err)
+		return
+	}
+	if account != nil {
+		if err := s.db.DeleteCalendarAccount(r.Context(), user.ID, account.ID); err != nil {
+			s.internal(w, r, "disconnect calendar", err)
+			return
+		}
+	}
+	w.WriteHeader(http.StatusNoContent)
+}
+
+// --- what the grid reads -----------------------------------------------------------
+
+type calendarEventsJSON struct {
+	Events []store.CalendarEvent `json:"events"`
+	// From and To are the window verdande holds a copy of, not the window that was
+	// asked for. A grid that has paged past it gets no events, and an empty answer
+	// with no explanation is a calendar quietly claiming a day is clear.
+	From string `json:"from"`
+	To   string `json:"to"`
+}
+
+func (s *Server) handleCalendarEvents(w http.ResponseWriter, r *http.Request) {
+	user := userFrom(r.Context())
+	from := r.URL.Query().Get("from")
+	to := r.URL.Query().Get("to")
+
+	fields := map[string]string{}
+	if !validDay(from) {
+		fields["from"] = "must be a date, as 2026-08-20"
+	}
+	if !validDay(to) {
+		fields["to"] = "must be a date, as 2026-08-20"
+	}
+	if len(fields) > 0 {
+		writeFieldErrors(w, fields)
+		return
+	}
+
+	events, err := s.db.CalendarEvents(r.Context(), user.ID, from, to)
+	if err != nil {
+		s.internal(w, r, "calendar events", err)
+		return
+	}
+	if events == nil {
+		events = []store.CalendarEvent{}
+	}
+	windowFrom, windowTo := calendarWindow(time.Now())
+	writeJSON(w, http.StatusOK, calendarEventsJSON{
+		Events: events, From: windowFrom, To: windowTo,
+	})
+}
+
+// handleCalendarSyncNow refreshes immediately, so somebody who has just connected
+// can see it work rather than wondering whether it did.
+func (s *Server) handleCalendarSyncNow(w http.ResponseWriter, r *http.Request) {
+	user := userFrom(r.Context())
+
+	// A budget of its own, well under what sits in front of this server. An unset
+	// budget is not a budget of nothing: a zero here would expire the context
+	// before the first call and make every sync a silent no-op.
+	budget := s.cfg.CalendarSyncBudget
+	if budget <= 0 {
+		budget = defaultCalendarSyncBudget
+	}
+	ctx, cancel := context.WithTimeout(r.Context(), budget)
+	defer cancel()
+
+	count, err := s.SyncCalendars(ctx, user)
+	if err != nil {
+		if errors.Is(err, context.DeadlineExceeded) {
+			// Not a failure: Google is slow or busy, some calendars were read, and
+			// the rest arrive on the next run. Every calendar is committed as it is
+			// read, so a short budget is a shorter run rather than a lost one.
+			writeJSON(w, http.StatusOK, map[string]any{"events": count, "partial": true})
+			return
+		}
+		s.upstream(w, r, CodeCalendarFailed, "sync calendar", err)
+		return
+	}
+	writeJSON(w, http.StatusOK, map[string]int{"events": count})
+}
+
+// SyncCalendars refreshes every calendar this person has chosen to see.
+//
+// Returns how many events were written. Also used by the background job, which is
+// why it takes a context and a user rather than a request.
+func (s *Server) SyncCalendars(ctx context.Context, user *store.User) (int, error) {
+	account, err := s.db.CalendarAccountFor(ctx, user.ID, calendarProviderName)
+	if err != nil {
+		return 0, err
+	}
+	if account == nil || account.RefreshToken == "" {
+		return 0, nil // not connected; nothing to do and nothing to complain about
+	}
+
+	// The same guard the mailboxes have, for the same reason: a press of "fetch
+	// now" during the sweep would otherwise have two runs replacing the same window
+	// at once, and the loser's delete would land after the winner's insert.
+	unlock := s.lockSync("calendar:" + account.ID)
+	defer unlock()
+	if fresh, err := s.db.CalendarAccountFor(ctx, user.ID, calendarProviderName); err == nil && fresh != nil {
+		account = fresh
+	}
+
+	access, err := s.calendarAccessToken(ctx, account)
+	if err != nil {
+		return 0, err
+	}
+	client := s.calendarClient(access)
+
+	// The list first, so a calendar added or renamed since the last run is drawn
+	// under its new name and one that has gone stops being drawn at all.
+	calendars, err := s.calendarList(ctx, client, account)
+	if err != nil {
+		return 0, s.forgetIfRevoked(ctx, user, account, err)
+	}
+
+	from, to := calendarWindow(time.Now())
+	written := 0
+	for _, calendar := range calendars {
+		if !calendar.Shown {
+			continue
+		}
+		// A spent budget ends the run rather than turning into a failed fetch per
+		// calendar, logged one at a time.
+		if ctx.Err() != nil {
+			return written, ctx.Err()
+		}
+		events, err := client.Events(ctx, calendar.RemoteID, from, to)
+		if err != nil {
+			if errors.Is(err, gcal.ErrUnauthorized) {
+				return written, s.forgetIfRevoked(ctx, user, account, err)
+			}
+			// One calendar somebody was unshared from must not stop the others.
+			s.log.Warn("calendar events", "err", err, "calendar", calendar.Name)
+			continue
+		}
+
+		rows := make([]store.CalendarEvent, 0, len(events))
+		for _, e := range events {
+			rows = append(rows, store.CalendarEvent{
+				RemoteID: e.ID, Summary: e.Summary,
+				StartsAt: e.StartsAt, EndsAt: e.EndsAt,
+				StartDay: e.StartDay, EndDay: e.EndDay,
+				AllDay: e.AllDay, Location: e.Location, URL: e.URL,
+			})
+		}
+		if err := s.db.ReplaceCalendarEvents(ctx, calendar.ID, from, to, rows); err != nil {
+			return written, err
+		}
+		written += len(rows)
+	}
+
+	if err := s.db.MarkCalendarSynced(ctx, account.ID, time.Now()); err != nil {
+		return written, err
+	}
+	return written, nil
+}
+
+// calendarAccessToken returns a usable access token, refreshing only when the one
+// held has actually expired.
+func (s *Server) calendarAccessToken(ctx context.Context, account *store.CalendarAccount) (string, error) {
+	if account.AccessToken != "" && account.ExpiresAt.After(time.Now()) {
+		return account.AccessToken, nil
+	}
+	token, err := s.calendarConfig(ctx).Refresh(ctx, account.RefreshToken)
+	if err != nil {
+		return "", err
+	}
+	account.AccessToken = token.AccessToken
+	account.ExpiresAt = token.ExpiresAt
+	if err := s.db.SaveCalendarAccount(ctx, account); err != nil {
+		return "", err
+	}
+	return account.AccessToken, nil
+}
+
+// refreshCalendarList fetches the calendar list with a token it obtains itself.
+// Used by the paths that have an account but no client yet — connecting, and the
+// status endpoint correcting an empty list.
+func (s *Server) refreshCalendarList(ctx context.Context, account *store.CalendarAccount) ([]store.Calendar, error) {
+	access, err := s.calendarAccessToken(ctx, account)
+	if err != nil {
+		return nil, err
+	}
+	return s.calendarList(ctx, s.calendarClient(access), account)
+}
+
+// calendarList writes what the provider says and returns what is stored, which is
+// not the same list: the provider says what exists, and only verdande knows which
+// of them somebody chose to look at.
+func (s *Server) calendarList(ctx context.Context, client *gcal.Client, account *store.CalendarAccount) ([]store.Calendar, error) {
+	remote, err := client.Calendars(ctx)
+	if err != nil {
+		return nil, err
+	}
+
+	list := make([]store.Calendar, 0, len(remote))
+	for _, c := range remote {
+		list = append(list, store.Calendar{
+			RemoteID: c.ID, Name: c.Name, Colour: c.Colour,
+			TimeZone: c.TimeZone, Primary: c.Primary, Writable: c.Owner,
+		})
+		// The primary calendar is the account, and its id is the address. It is the
+		// only place the connected account names itself without a second scope —
+		// asking for a profile scope to learn an address already in the answer would
+		// be one more thing on the consent screen for nothing.
+		if c.Primary && account.Account == "" {
+			account.Account = c.ID
+			if err := s.db.SaveCalendarAccount(ctx, account); err != nil {
+				return nil, err
+			}
+		}
+	}
+	if err := s.db.ReplaceCalendars(ctx, account.ID, list); err != nil {
+		return nil, err
+	}
+	return s.db.Calendars(ctx, account.ID)
+}
+
+// forgetIfRevoked disconnects when Google says the grant is gone, and passes every
+// other failure through untouched.
+//
+// The distinction is the point. A revoked account polled every ten minutes for ever
+// is a log line a week long and a connection the person believes they removed; a
+// Google that is merely down is one that will answer next time.
+func (s *Server) forgetIfRevoked(ctx context.Context, user *store.User, account *store.CalendarAccount, err error) error {
+	if errors.Is(err, gcal.ErrUnauthorized) {
+		s.log.Info("calendar access was revoked; disconnecting", "user", user.ID)
+		_ = s.db.DeleteCalendarAccount(ctx, user.ID, account.ID)
+	}
+	return err
+}
+
+// calendarWindow is the span verdande keeps a copy of, measured from today.
+//
+// Built from the calendar date rather than by truncating the instant: Truncate
+// rounds against the Unix epoch, which is midnight UTC, and in Copenhagen that is
+// two in the morning — so for two hours of every summer day the window would start
+// and end a day out.
+func calendarWindow(now time.Time) (string, string) {
+	day := time.Date(now.Year(), now.Month(), now.Day(), 0, 0, 0, 0, now.Location())
+	return day.AddDate(0, 0, -calendarWindowBack).Format(calendarDateLayout),
+		day.AddDate(0, 0, calendarWindowAhead).Format(calendarDateLayout)
+}
+
+func validDay(s string) bool {
+	_, err := time.Parse(calendarDateLayout, s)
+	return err == nil
+}
@@ -0,0 +1,471 @@
+package httpapi
+
+import (
+	"encoding/json"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/kristianwind/verdande/internal/config"
+	"github.com/kristianwind/verdande/internal/store"
+)
+
+// fakeCalendarGoogle stands in for the parts of Google this feature touches: the
+// token endpoint, the calendar list and one calendar's events.
+//
+// There is no other way to exercise any of it. The real thing needs a registered
+// OAuth client, an account and somebody's consent, and none of the three can be had
+// inside a test — so the shapes Google returns are written down and the behaviour
+// is checked against them, the way internal/imap is checked against go-imap's own
+// in-process server.
+type fakeCalendarGoogle struct {
+	*httptest.Server
+	// refreshes counts token refreshes, so a test can prove one is not made for a
+	// token that has not expired.
+	refreshes int
+	// refuse makes every API call answer 401, which is what a revoked grant does.
+	refuse bool
+	events map[string][]map[string]any
+}
+
+func newFakeCalendarGoogle(t *testing.T) *fakeCalendarGoogle {
+	t.Helper()
+	g := &fakeCalendarGoogle{events: map[string][]map[string]any{}}
+	g.Server = httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "application/json")
+		switch {
+		case r.URL.Path == "/token":
+			g.refreshes++
+			_ = json.NewEncoder(w).Encode(map[string]any{
+				"access_token": "ya29.fresh", "refresh_token": "1//0-refresh",
+				"expires_in": 3600,
+			})
+		case g.refuse:
+			http.Error(w, `{"error":"invalid_credentials"}`, http.StatusUnauthorized)
+		case strings.HasPrefix(r.URL.Path, "/users/me/calendarList"):
+			_ = json.NewEncoder(w).Encode(map[string]any{"items": []map[string]any{
+				{"id": "[email protected]", "summary": "[email protected]", "primary": true,
+					"accessRole": "owner", "backgroundColor": "#3f51b5",
+					"timeZone": "Europe/Copenhagen"},
+				{"id": "fam", "summary": "Familien", "accessRole": "reader",
+					"backgroundColor": "#0b8043"},
+			}})
+		case strings.HasPrefix(r.URL.Path, "/calendars/"):
+			id := strings.TrimSuffix(strings.TrimPrefix(r.URL.Path, "/calendars/"), "/events")
+			items := g.events[id]
+			if items == nil {
+				items = []map[string]any{}
+			}
+			_ = json.NewEncoder(w).Encode(map[string]any{"items": items})
+		default:
+			http.Error(w, "unexpected "+r.URL.Path, http.StatusNotFound)
+		}
+	}))
+	t.Cleanup(g.Close)
+	return g
+}
+
+// connectedCalendar returns a server with a calendar account already connected —
+// the state the OAuth callback leaves behind, without the consent screen nothing
+// can automate.
+func connectedCalendar(t *testing.T, g *fakeCalendarGoogle, tune func(*config.Config)) (*testServer, *store.User) {
+	t.Helper()
+	ts := newTestServerWith(t, func(cfg *config.Config) {
+		cfg.GmailClientID = "test-client"
+		cfg.GmailClientSecret = "test-secret"
+		cfg.GoogleTokenURL = g.URL + "/token"
+		cfg.CalendarAPIURL = g.URL
+		if tune != nil {
+			tune(cfg)
+		}
+	})
+	ts.bootstrap(t)
+
+	user, err := ts.db.UserByEmail(t.Context(), "[email protected]")
+	if err != nil {
+		t.Fatal(err)
+	}
+	account := &store.CalendarAccount{
+		UserID: user.ID, Provider: "google", RefreshToken: "1//0-refresh",
+	}
+	if err := ts.db.SaveCalendarAccount(t.Context(), account); err != nil {
+		t.Fatal(err)
+	}
+	return ts, user
+}
+
+// The scope on the consent screen is what somebody agrees to. It has to be the
+// read-only one, and the redirect has to be the calendar's own — sharing Gmail's
+// would put "which token store do I write" behind a lookup.
+func TestAuthorizeAsksForReadOnlyCalendar(t *testing.T) {
+	g := newFakeCalendarGoogle(t)
+	ts, _ := connectedCalendar(t, g, nil)
+
+	resp, body := ts.do(t, "POST", "/api/v1/calendar/authorize", nil)
+	if resp.StatusCode != http.StatusOK {
+		t.Fatalf("status %d, body %v", resp.StatusCode, body)
+	}
+	url, _ := body["url"].(string)
+	for _, want := range []string{
+		"scope=" + "https%3A%2F%2Fwww.googleapis.com%2Fauth%2Fcalendar.readonly",
+		"%2Foauth%2Fcalendar%2Fcallback",
+		"access_type=offline",
+		"prompt=consent",
+	} {
+		if !strings.Contains(url, want) {
+			t.Errorf("the authorisation URL is missing %q:\n%s", want, url)
+		}
+	}
+	if strings.Contains(url, "calendar.events&") || strings.Contains(url, "auth%2Fcalendar&") {
+		t.Errorf("a writing scope was asked for:\n%s", url)
+	}
+}
+
+// Without a registered client there is nothing to connect through, and the answer
+// has to say that rather than "that already exists".
+func TestAuthorizeWithoutAClientSaysSo(t *testing.T) {
+	ts := newTestServer(t)
+	ts.bootstrap(t)
+
+	resp, body := ts.do(t, "POST", "/api/v1/calendar/authorize", nil)
+	if resp.StatusCode != http.StatusConflict {
+		t.Fatalf("status %d, want 409", resp.StatusCode)
+	}
+	if body["code"] != CodeGmailNotConfigured {
+		t.Errorf("code = %v, want %q", body["code"], CodeGmailNotConfigured)
+	}
+}
+
+// The whole path, minus the consent screen: sync fetches the list, refreshes the
+// events of what was chosen, and the grid endpoint answers with them.
+func TestSyncFetchesTheChosenCalendarsAndTheGridReadsThem(t *testing.T) {
+	g := newFakeCalendarGoogle(t)
+	g.events["fam"] = []map[string]any{
+		{"id": "e1", "summary": "Bestyrelsesmøde", "htmlLink": "https://calendar.google.com/e1",
+			"start": map[string]string{"dateTime": "2026-08-20T14:00:00+02:00"},
+			"end":   map[string]string{"dateTime": "2026-08-20T15:30:00+02:00"}},
+	}
+	g.events["[email protected]"] = []map[string]any{
+		{"id": "e2", "summary": "Skal ikke med",
+			"start": map[string]string{"date": "2026-08-21"},
+			"end":   map[string]string{"date": "2026-08-22"}},
+	}
+	ts, user := connectedCalendar(t, g, nil)
+
+	// The list arrives on the first look at the settings page, which is what
+	// somebody would be doing at this point.
+	resp, body := ts.do(t, "GET", "/api/v1/calendar", nil)
+	if resp.StatusCode != http.StatusOK {
+		t.Fatalf("status %d, body %v", resp.StatusCode, body)
+	}
+	if body["connected"] != true {
+		t.Fatalf("not reported as connected: %v", body)
+	}
+	if body["read_only"] != true {
+		t.Error("the connection did not say it is read-only; an interface that looks " +
+			"editable is one somebody will try to edit")
+	}
+	// The primary calendar's id is the address, which is how the account names
+	// itself without asking for a profile scope as well.
+	if body["account"] != "[email protected]" {
+		t.Errorf("account = %v", body["account"])
+	}
+
+	list, _ := body["calendars"].([]any)
+	if len(list) != 2 {
+		t.Fatalf("got %d calendars, want 2: %v", len(list), body["calendars"])
+	}
+	var famID string
+	for _, raw := range list {
+		c := raw.(map[string]any)
+		if c["shown"] == true {
+			t.Errorf("%v was shown without anybody choosing it", c["name"])
+		}
+		if c["remote_id"] == "fam" {
+			famID = c["id"].(string)
+		}
+	}
+
+	// Nothing is chosen, so a sync writes nothing: an account with a dozen shared
+	// calendars must not fill somebody's grid the moment it is connected.
+	resp, body = ts.do(t, "POST", "/api/v1/calendar/sync", nil)
+	if resp.StatusCode != http.StatusOK || body["events"] != float64(0) {
+		t.Fatalf("an unchosen calendar was fetched: %d %v", resp.StatusCode, body)
+	}
+
+	resp, _ = ts.do(t, "PUT", "/api/v1/calendar/calendars",
+		map[string]any{"shown": []string{famID}})
+	if resp.StatusCode != http.StatusNoContent {
+		t.Fatalf("choosing a calendar: status %d", resp.StatusCode)
+	}
+
+	resp, body = ts.do(t, "POST", "/api/v1/calendar/sync", nil)
+	if resp.StatusCode != http.StatusOK {
+		t.Fatalf("sync: status %d, body %v", resp.StatusCode, body)
+	}
+	if body["events"] != float64(1) {
+		t.Fatalf("events = %v, want 1 — only the chosen calendar", body["events"])
+	}
+
+	resp, body = ts.do(t, "GET",
+		"/api/v1/calendar/events?from=2026-08-01&to=2026-08-31", nil)
+	if resp.StatusCode != http.StatusOK {
+		t.Fatalf("events: status %d, body %v", resp.StatusCode, body)
+	}
+	events, _ := body["events"].([]any)
+	if len(events) != 1 {
+		t.Fatalf("got %d events, want 1: %v", len(events), body["events"])
+	}
+	event := events[0].(map[string]any)
+	if event["summary"] != "Bestyrelsesmøde" || event["start_day"] != "2026-08-20" {
+		t.Errorf("the event came back as %v", event)
+	}
+	// The calendar's colour rides along, or the chip has to ask for it per row.
+	if event["colour"] != "#0b8043" {
+		t.Errorf("colour = %v; two calendars in one grid are told apart by it", event["colour"])
+	}
+	// The window verdande holds is stated, so a grid paged past it can say so
+	// rather than showing an empty month it cannot explain.
+	if body["from"] == "" || body["to"] == "" {
+		t.Error("the answer does not say which window it covers")
+	}
+
+	// And it is one person's calendar. Somebody else on the same instance sees
+	// nothing of it.
+	other := ts.newUser(t, "[email protected]", "Andreas")
+	_, body = other.do(t, "GET", "/api/v1/calendar/events?from=2026-08-01&to=2026-08-31", nil)
+	if events, _ := body["events"].([]any); len(events) != 0 {
+		t.Errorf("somebody else's calendar was visible: %v", body["events"])
+	}
+	_ = user
+}
+
+// A token that has not expired must not be traded in for another. Refreshing on
+// every run burns the quota and makes the failure mode of a bad refresh token
+// arrive on every sweep rather than once an hour.
+func TestAFreshTokenIsNotRefreshed(t *testing.T) {
+	g := newFakeCalendarGoogle(t)
+	ts, user := connectedCalendar(t, g, nil)
+
+	account, err := ts.db.CalendarAccountFor(t.Context(), user.ID, "google")
+	if err != nil {
+		t.Fatal(err)
+	}
+	account.AccessToken = "ya29.still-good"
+	account.ExpiresAt = time.Now().Add(time.Hour)
+	if err := ts.db.SaveCalendarAccount(t.Context(), account); err != nil {
+		t.Fatal(err)
+	}
+
+	if resp, body := ts.do(t, "POST", "/api/v1/calendar/sync", nil); resp.StatusCode != http.StatusOK {
+		t.Fatalf("sync: status %d, body %v", resp.StatusCode, body)
+	}
+	if g.refreshes != 0 {
+		t.Errorf("the token was refreshed %d times while it was still good", g.refreshes)
+	}
+
+	// And an expired one is.
+	account.ExpiresAt = time.Now().Add(-time.Minute)
+	if err := ts.db.SaveCalendarAccount(t.Context(), account); err != nil {
+		t.Fatal(err)
+	}
+	if resp, body := ts.do(t, "POST", "/api/v1/calendar/sync", nil); resp.StatusCode != http.StatusOK {
+		t.Fatalf("sync: status %d, body %v", resp.StatusCode, body)
+	}
+	if g.refreshes != 1 {
+		t.Errorf("an expired token was refreshed %d times, want 1", g.refreshes)
+	}
+}
+
+// Access revoked at Google's end is a connection that has ended, not a failure to
+// retry. Polling it every fifteen minutes for ever is a week of log lines and a
+// connection the person believes they removed.
+func TestRevokedAccessDisconnects(t *testing.T) {
+	g := newFakeCalendarGoogle(t)
+	ts, user := connectedCalendar(t, g, nil)
+
+	account, _ := ts.db.CalendarAccountFor(t.Context(), user.ID, "google")
+	account.AccessToken = "ya29.revoked"
+	account.ExpiresAt = time.Now().Add(time.Hour)
+	if err := ts.db.SaveCalendarAccount(t.Context(), account); err != nil {
+		t.Fatal(err)
+	}
+	g.refuse = true
+
+	resp, body := ts.do(t, "POST", "/api/v1/calendar/sync", nil)
+	if resp.StatusCode != StatusUpstreamRefused {
+		t.Fatalf("status %d, want %d — Google saying no is not this server breaking",
+			resp.StatusCode, StatusUpstreamRefused)
+	}
+	if body["code"] != CodeCalendarFailed {
+		t.Errorf("code = %v, want %q — `internal_error` is shown as a generic sentence, "+
+			"which throws the diagnosis away", body["code"], CodeCalendarFailed)
+	}
+
+	gone, err := ts.db.CalendarAccountFor(t.Context(), user.ID, "google")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if gone != nil {
+		t.Error("the connection is still there after Google refused the token")
+	}
+
+	// And the failure is in the error log, which is the point of having one: a
+	// sync that has been failing for a week is invisible otherwise.
+	_, logged := ts.do(t, "GET", "/api/v1/errors", nil)
+	rows, _ := logged["errors"].([]any)
+	if len(rows) == 0 {
+		t.Fatal("nothing was recorded")
+	}
+	if row := rows[0].(map[string]any); row["what"] != "sync calendar" {
+		t.Errorf("what = %v, want \"sync calendar\"", row["what"])
+	}
+}
+
+// Disconnecting takes the copy with it. None of it is the person's own work, and
+// a calendar left behind after the account is gone is a frozen lie about a day.
+func TestDisconnectingRemovesTheEvents(t *testing.T) {
+	g := newFakeCalendarGoogle(t)
+	g.events["fam"] = []map[string]any{
+		{"id": "e1", "summary": "Møde",
+			"start": map[string]string{"date": "2026-08-20"},
+			"end":   map[string]string{"date": "2026-08-21"}},
+	}
+	ts, user := connectedCalendar(t, g, nil)
+
+	ts.do(t, "GET", "/api/v1/calendar", nil)
+	account, _ := ts.db.CalendarAccountFor(t.Context(), user.ID, "google")
+	calendars, _ := ts.db.Calendars(t.Context(), account.ID)
+	var famID string
+	for _, c := range calendars {
+		if c.RemoteID == "fam" {
+			famID = c.ID
+		}
+	}
+	ts.do(t, "PUT", "/api/v1/calendar/calendars", map[string]any{"shown": []string{famID}})
+	ts.do(t, "POST", "/api/v1/calendar/sync", nil)
+
+	if resp, _ := ts.do(t, "DELETE", "/api/v1/calendar", nil); resp.StatusCode != http.StatusNoContent {
+		t.Fatalf("disconnect: status %d", resp.StatusCode)
+	}
+
+	_, body := ts.do(t, "GET", "/api/v1/calendar/events?from=2026-08-01&to=2026-08-31", nil)
+	if events, _ := body["events"].([]any); len(events) != 0 {
+		t.Errorf("events survived the disconnect: %v", body["events"])
+	}
+	_, body = ts.do(t, "GET", "/api/v1/calendar", nil)
+	if body["connected"] != false {
+		t.Error("still reported as connected")
+	}
+}
+
+// A range that is not a date has to be refused, not guessed at. An empty `from`
+// compared as a string matches everything before it, which is a grid quietly
+// answering a question nobody asked.
+func TestEventsRefuseARangeThatIsNotADate(t *testing.T) {
+	g := newFakeCalendarGoogle(t)
+	ts, _ := connectedCalendar(t, g, nil)
+
+	for _, query := range []string{
+		"", "?from=2026-08-01", "?from=&to=2026-08-31",
+		"?from=i+morgen&to=2026-08-31", "?from=2026-08-01&to=2026-13-40",
+	} {
+		resp, body := ts.do(t, "GET", "/api/v1/calendar/events"+query, nil)
+		if resp.StatusCode != http.StatusUnprocessableEntity {
+			t.Errorf("%q: status %d, want 422 (%v)", query, resp.StatusCode, body)
+		}
+	}
+}
+
+// A person with no calendar connected still opens the view. It has to answer, and
+// answer emptily, rather than fail — the grid is also verdande's own tasks, and
+// they must not disappear because Google is not set up.
+func TestTheGridAnswersWithNoCalendarConnected(t *testing.T) {
+	ts := newTestServer(t)
+	ts.bootstrap(t)
+
+	resp, body := ts.do(t, "GET", "/api/v1/calendar/events?from=2026-08-01&to=2026-08-31", nil)
+	if resp.StatusCode != http.StatusOK {
+		t.Fatalf("status %d, body %v", resp.StatusCode, body)
+	}
+	if events, ok := body["events"].([]any); !ok || len(events) != 0 {
+		t.Errorf("events = %v, want an empty list rather than null", body["events"])
+	}
+
+	resp, body = ts.do(t, "GET", "/api/v1/calendar", nil)
+	if resp.StatusCode != http.StatusOK || body["connected"] != false {
+		t.Fatalf("status %d, body %v", resp.StatusCode, body)
+	}
+	if body["has_client"] != false {
+		t.Error("an instance with no OAuth registration claimed to have one; the page " +
+			"would offer a button that answers 409")
+	}
+	// Spelled out even when nothing is connected: it is what has to be registered
+	// with Google, and it is the single most likely thing to be wrong.
+	if uri, _ := body["redirect_uri"].(string); !strings.HasSuffix(uri, "/oauth/calendar/callback") {
+		t.Errorf("redirect_uri = %q", uri)
+	}
+}
+
+// A slow Google must not hold the request open until something in front of this
+// server gives up on it and answers with its own HTML.
+func TestASlowCalendarDoesNotHangTheRequest(t *testing.T) {
+	blocked := make(chan struct{})
+	defer close(blocked)
+	slow := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		select {
+		case <-blocked:
+		case <-r.Context().Done():
+		}
+	}))
+	defer slow.Close()
+
+	ts := newTestServerWith(t, func(cfg *config.Config) {
+		cfg.GmailClientID = "test-client"
+		cfg.GmailClientSecret = "test-secret"
+		cfg.GoogleTokenURL = slow.URL + "/token"
+		cfg.CalendarAPIURL = slow.URL
+		// A second rather than the real twenty-five: what is being tested is that a
+		// budget is applied at all, and spending the production one on every run
+		// would put half a minute into the suite to learn the same thing.
+		cfg.CalendarSyncBudget = time.Second
+	})
+	ts.bootstrap(t)
+
+	user, err := ts.db.UserByEmail(t.Context(), "[email protected]")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := ts.db.SaveCalendarAccount(t.Context(), &store.CalendarAccount{
+		UserID: user.ID, Provider: "google", RefreshToken: "r",
+		AccessToken: "a", ExpiresAt: time.Now().Add(time.Hour),
+	}); err != nil {
+		t.Fatal(err)
+	}
+
+	// Its own client, because the shared one gives up after ten seconds — which is
+	// shorter than the budget being tested and would prove nothing either way.
+	req, _ := http.NewRequest("POST", ts.URL+"/api/v1/calendar/sync", nil)
+	req.Header.Set("Sec-Fetch-Site", "same-origin")
+	for _, c := range ts.client.Jar.Cookies(mustParse(t, ts.URL)) {
+		req.AddCookie(c)
+	}
+
+	started := time.Now()
+	resp, err := (&http.Client{Timeout: 90 * time.Second}).Do(req)
+	if err != nil {
+		t.Fatalf("the request never came back (%v after %s); the sync has no budget of its "+
+			"own, and whatever sits in front of this server answers for it",
+			err, time.Since(started).Round(time.Second))
+	}
+	defer resp.Body.Close()
+
+	if took := time.Since(started); took > 10*time.Second {
+		t.Errorf("the sync took %s; the budget is not being applied", took.Round(time.Second))
+	}
+	if resp.StatusCode >= 500 {
+		t.Errorf("status %d — a slow Google is not this server breaking", resp.StatusCode)
+	}
+}
@@ -63,6 +63,11 @@ const (
 	// diagnosis — a wrong app password, a host that is not listening, a folder that
 	// is not there — and it says it in its own words.
 	CodeMailboxFailed = "mailbox_failed"
+
+	// And for a calendar read from Google. Its own code rather than the Gmail one,
+	// because the sentence the interface wraps it in names where it came from — and
+	// "Gmail said no" about a calendar sends somebody to the wrong panel.
+	CodeCalendarFailed = "calendar_failed"
 )

 // errLastAdmin is returned to the caller that already wrote the response, so it
@@ -25,18 +25,16 @@ const defaultGmailSyncBudget = 25 * time.Second
 // to redeploy a container to paste a client id.
 // gmailClient is the API client, pointed wherever the config says Google is.
 func (s *Server) gmailClient(accessToken string) *gmail.Client {
-	return gmail.NewClient(accessToken).At(gmail.Endpoints{
-		Token: s.cfg.GmailTokenURL, API: s.cfg.GmailAPIURL,
-	})
+	return gmail.NewClient(accessToken).At(s.cfg.GmailAPIURL)
 }

 func (s *Server) gmailConfig(ctx context.Context) gmail.Config {
-	endpoints := gmail.Endpoints{Token: s.cfg.GmailTokenURL, API: s.cfg.GmailAPIURL}
 	cfg := gmail.Config{
 		ClientID:     s.cfg.GmailClientID,
 		ClientSecret: s.cfg.GmailClientSecret,
 		RedirectURL:  s.cfg.GmailRedirectURL(),
-		Endpoints:    endpoints,
+		Scope:        gmail.Scope,
+		TokenURL:     s.cfg.GoogleTokenURL,
 	}
 	if cfg.ClientID != "" && cfg.ClientSecret != "" {
 		return cfg
@@ -271,7 +269,7 @@ func (s *Server) SyncGmail(ctx context.Context, user *store.User) (int, error) {
 		// The same guard as the mailboxes read over IMAP, for the same reason: a
 		// press of "Fetch now" during the sweep would otherwise make two runs from
 		// one marker.
-		unlock := s.lockMailbox(box.ID)
+		unlock := s.lockSync(box.ID)
 		defer unlock()
 		if fresh, err := s.db.MailboxOfKind(ctx, user.ID, "gmail"); err == nil && fresh != nil {
 			box = fresh
@@ -29,7 +29,7 @@ func TestAGmailFailureSaysWhatGmailSaidAndIsRecorded(t *testing.T) {
 	ts := newTestServerWith(t, func(cfg *config.Config) {
 		cfg.GmailClientID = "test-client"
 		cfg.GmailClientSecret = "test-secret"
-		cfg.GmailTokenURL = google.URL + "/token"
+		cfg.GoogleTokenURL = google.URL + "/token"
 		cfg.GmailAPIURL = google.URL
 	})
 	ts.bootstrap(t)
@@ -97,7 +97,7 @@ func TestASlowMailboxDoesNotHangTheRequest(t *testing.T) {
 	ts := newTestServerWith(t, func(cfg *config.Config) {
 		cfg.GmailClientID = "test-client"
 		cfg.GmailClientSecret = "test-secret"
-		cfg.GmailTokenURL = google.URL + "/token"
+		cfg.GoogleTokenURL = google.URL + "/token"
 		cfg.GmailAPIURL = google.URL
 		// A second rather than the real twenty-five: what is being tested is that a
 		// budget is applied at all, and spending the production one on every run
@@ -143,7 +143,7 @@ func (s *Server) SyncMailbox(ctx context.Context, user *store.User, m *store.Mai
 	// One reader of this mailbox at a time. Held for the whole run, marker and all:
 	// releasing before the marker is written would leave exactly the gap this is
 	// here to close.
-	unlock := s.lockMailbox(m.ID)
+	unlock := s.lockSync(m.ID)
 	defer unlock()

 	// Re-read under the lock. The row that came in may have been fetched before the
@@ -250,8 +250,14 @@ func (s *Server) SyncMailbox(ctx context.Context, user *store.User, m *store.Mai
 	return created, nil
 }

-// lockMailbox serialises one mailbox against itself and returns the release.
-func (s *Server) lockMailbox(id string) func() {
+// lockSync serialises one thing that polls against itself and returns the release.
+//
+// A mailbox to begin with; a calendar connection now takes the same lock under a
+// key of its own. Two runs at once — somebody pressing "fetch now" while the sweep
+// is in the middle of the same thing — both start from the state as it was, and
+// the loser writes last. For a mailbox that made forty copies of one mail in a
+// second; for a calendar it would be a window deleted after it was refilled.
+func (s *Server) lockSync(id string) func() {
 	value, _ := s.syncing.LoadOrStore(id, &sync.Mutex{})
 	mu := value.(*sync.Mutex)
 	mu.Lock()
@@ -102,7 +102,7 @@ func TestTwoRunsOfOneMailboxDoNotOverlap(t *testing.T) {
 	// Stands in for a run: takes the lock, notes how many are inside, and holds it
 	// until told to let go.
 	run := func(done chan<- struct{}) {
-		unlock := srv.lockMailbox("box-1")
+		unlock := srv.lockSync("box-1")
 		mu.Lock()
 		inside++
 		if inside > most {
@@ -136,10 +136,10 @@ func TestTwoRunsOfOneMailboxDoNotOverlap(t *testing.T) {

 	// And two different mailboxes must not wait for each other: one slow host is
 	// not everybody's problem.
-	a := srv.lockMailbox("box-a")
+	a := srv.lockSync("box-a")
 	done := make(chan struct{})
 	go func() {
-		srv.lockMailbox("box-b")()
+		srv.lockSync("box-b")()
 		close(done)
 	}()
 	select {
@@ -133,6 +133,12 @@ func New(cfg *config.Config, db *store.DB, log *slog.Logger, web fs.FS) *Server
 	r.Group(func(r chi.Router) {
 		r.Use(s.requireAuth)
 		r.Get("/oauth/gmail/callback", s.handleGmailCallback)
+		// The calendar comes back on a URI of its own rather than sharing Gmail's.
+		// One callback deciding from stored state which of the two flows had
+		// returned would put the choice of *which token store to write* behind a
+		// lookup — and when that goes wrong it goes wrong by overwriting a working
+		// Gmail connection with calendar tokens.
+		r.Get("/oauth/calendar/callback", s.handleCalendarCallback)
 	})
 	r.Route("/caldav", s.caldavRoutes)

@@ -333,6 +339,19 @@ func New(cfg *config.Config, db *store.DB, log *slog.Logger, web fs.FS) *Server
 				})
 			})

+			// A calendar read from somewhere else, laid under verdande's own dated
+			// tasks. Read-only, so there is no write here to gate: the events are a
+			// copy of somebody else's calendar, and the only thing a person decides
+			// is which of them to look at.
+			r.Route("/calendar", func(r chi.Router) {
+				r.Get("/", s.handleGetCalendar)
+				r.Put("/calendars", s.handleSetCalendars)
+				r.Delete("/", s.handleDisconnectCalendar)
+				r.Post("/authorize", s.handleCalendarAuthorize)
+				r.Post("/sync", s.handleCalendarSyncNow)
+				r.Get("/events", s.handleCalendarEvents)
+			})
+
 			r.Route("/import", func(r chi.Router) {
 				r.Post("/todoist", s.handleImportTodoist)
 				r.Post("/csv", s.handleImportCSV)
@@ -41,6 +41,10 @@ type Runner struct {
 	// reason as SyncGmail: it owns turning a message into a task.
 	SyncMailbox func(ctx context.Context, user *store.User, m *store.Mailbox) (int, error)

+	// SyncCalendars refreshes one person's connected calendars. Supplied the same
+	// way and for the same reason: the HTTP layer owns the token refresh.
+	SyncCalendars func(ctx context.Context, user *store.User) (int, error)
+
 	// Push delivers a notification to somebody's devices. Supplied by the HTTP
 	// layer, which owns the VAPID keys and the subscription list.
 	Push func(userID, title, body, projectID string)
@@ -74,6 +78,13 @@ func (r *Runner) Start(ctx context.Context) {
 	// account for a to-do app. Ten minutes is fast enough for something somebody
 	// starred and slow enough not to look like abuse.
 	r.every(ctx, "mailboxes", 10*time.Minute, r.syncMailboxes)
+	// Fifteen minutes rather than ten. A calendar is not a mailbox: nothing here
+	// becomes a task, so being a quarter of an hour behind on a meeting next
+	// Tuesday costs nothing — and the "fetch now" button covers the one case where
+	// it matters, which is somebody who has just moved something and is looking at
+	// the grid to check. A person who has just connected does not wait for this
+	// either; connecting fetches the list, and the first sync is one click away.
+	r.every(ctx, "calendars", 15*time.Minute, r.syncCalendars)
 	// Checked hourly, sent at most daily — the same shape as the backup, and for
 	// the same reason: a container asleep at the scheduled minute would otherwise
 	// skip the day. SendBeacon decides whether a day has passed.
@@ -342,6 +353,44 @@ func (r *Runner) syncMailboxes(ctx context.Context) error {
 	return nil
 }

+// --- calendars ------------------------------------------------------------------------
+
+// syncCalendars refreshes everybody's connected calendars.
+//
+// Its own sweep rather than a branch inside the mailbox one. They share nothing
+// past the word "poll": that loop asks each mailbox how far it has read and makes
+// tasks, this one replaces a window of somebody else's events. Folding them
+// together would mean one interval for two questions that do not want the same
+// answer, and a Google that is down would count against a mailbox that is not.
+//
+// Nobody is waiting, so no budget of its own — the request handler has one because
+// a person is watching a spinner. One account that has gone quiet costs this run
+// its own timeout and nothing else: the loop moves on per person.
+func (r *Runner) syncCalendars(ctx context.Context) error {
+	if r.SyncCalendars == nil {
+		return nil
+	}
+	userIDs, err := r.db.UsersWithCalendars(ctx)
+	if err != nil {
+		return err
+	}
+	for _, id := range userIDs {
+		user, err := r.db.UserByID(ctx, id)
+		if err != nil || user == nil {
+			continue
+		}
+		written, err := r.SyncCalendars(ctx, user)
+		if err != nil {
+			r.log.Warn("calendar sync", "err", err, "user", id)
+			continue
+		}
+		if written > 0 {
+			r.log.Info("calendar refreshed", "user", id, "events", written)
+		}
+	}
+	return nil
+}
+
 // --- housekeeping -----------------------------------------------------------------

 func (r *Runner) emptyTrash(ctx context.Context) error {
@@ -0,0 +1,380 @@
+package store
+
+import (
+	"context"
+	"database/sql"
+	"fmt"
+	"time"
+)
+
+// CalendarAccount is one connected account belonging to one person.
+type CalendarAccount struct {
+	ID       string `json:"id"`
+	UserID   string `json:"-"`
+	Provider string `json:"provider"`
+	Account  string `json:"account,omitempty"`
+
+	RefreshToken string    `json:"-"` // never leaves the server
+	AccessToken  string    `json:"-"`
+	ExpiresAt    time.Time `json:"-"`
+
+	LastSyncAt time.Time `json:"last_sync_at,omitempty"`
+	CreatedAt  time.Time `json:"created_at"`
+}
+
+// Calendar is one calendar inside an account, shown or not.
+type Calendar struct {
+	ID        string `json:"id"`
+	AccountID string `json:"-"`
+	RemoteID  string `json:"remote_id"`
+	Name      string `json:"name"`
+	Colour    string `json:"colour,omitempty"`
+	TimeZone  string `json:"time_zone,omitempty"`
+	Primary   bool   `json:"primary"`
+	// Writable says the connected account could write to it. Nothing does — the
+	// scope is read-only — and it is stored so the day something can, the interface
+	// knows which calendars could even be offered.
+	Writable  bool `json:"writable"`
+	Shown     bool `json:"shown"`
+	SortOrder int  `json:"-"`
+}
+
+// CalendarEvent is one occurrence, in the shape a grid asks about: days at both
+// ends, inclusive.
+type CalendarEvent struct {
+	ID         string `json:"id"`
+	CalendarID string `json:"calendar_id"`
+	RemoteID   string `json:"-"`
+	Summary    string `json:"summary"`
+	StartsAt   string `json:"starts_at,omitempty"`
+	EndsAt     string `json:"ends_at,omitempty"`
+	StartDay   string `json:"start_day"`
+	EndDay     string `json:"end_day"`
+	AllDay     bool   `json:"all_day"`
+	Location   string `json:"location,omitempty"`
+	URL        string `json:"url,omitempty"`
+
+	// CalendarName and Colour ride along with the event rather than being looked up
+	// per row by the caller. Same reasoning as the assignee names on a task list:
+	// the chip has to be drawn in the calendar's own colour, and a second request
+	// per event to learn it is a request per event.
+	CalendarName string `json:"calendar_name,omitempty"`
+	Colour       string `json:"colour,omitempty"`
+}
+
+const calendarAccountColumns = `id, user_id, provider, account, refresh_token,
+	access_token, expires_at, last_sync_at, created_at`
+
+// CalendarAccountFor returns a person's connection to one provider, or nil.
+func (db *DB) CalendarAccountFor(ctx context.Context, userID, provider string) (*CalendarAccount, error) {
+	row := db.QueryRowContext(ctx, `SELECT `+calendarAccountColumns+`
+		FROM calendar_accounts WHERE user_id = ? AND provider = ?`, userID, provider)
+	a, err := db.scanCalendarAccount(row)
+	if err == sql.ErrNoRows {
+		return nil, nil
+	}
+	if err != nil {
+		return nil, err
+	}
+	return &a, nil
+}
+
+// SaveCalendarAccount writes one, sealing the two columns that must not travel
+// with a backup. Called by hand rather than by the settings tables' own seal,
+// which does not reach this table.
+func (db *DB) SaveCalendarAccount(ctx context.Context, a *CalendarAccount) error {
+	if a.ID == "" {
+		a.ID = NewID()
+	}
+	if a.Provider == "" {
+		a.Provider = "google"
+	}
+	if a.CreatedAt.IsZero() {
+		a.CreatedAt = time.Now()
+	}
+
+	refresh, err := db.sealValue(a.RefreshToken)
+	if err != nil {
+		return fmt.Errorf("seal refresh_token: %w", err)
+	}
+	access, err := db.sealValue(a.AccessToken)
+	if err != nil {
+		return fmt.Errorf("seal access_token: %w", err)
+	}
+
+	// The conflict is on the pair, not on the id: a reconnect builds a fresh
+	// struct with no id in it, and matching on the id would insert a second row
+	// that the unique index then refuses — which reads to the person as "connecting
+	// failed" when what happened is that it already had.
+	_, err = db.ExecContext(ctx, `
+		INSERT INTO calendar_accounts (`+calendarAccountColumns+`)
+		VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?)
+		ON CONFLICT (user_id, provider) DO UPDATE SET
+		    account = excluded.account,
+		    refresh_token = excluded.refresh_token,
+		    access_token = excluded.access_token,
+		    expires_at = excluded.expires_at,
+		    last_sync_at = excluded.last_sync_at`,
+		a.ID, a.UserID, a.Provider, a.Account, refresh, access,
+		unixOrZero(a.ExpiresAt), unixOrZero(a.LastSyncAt), a.CreatedAt.Unix())
+	if err != nil {
+		return err
+	}
+
+	// The row that is actually there wins. On a reconnect the insert above updated
+	// an existing row, so the id in hand is one nothing points at — and the
+	// calendars are hung off the id, so writing them against it would attach them
+	// to nothing.
+	return db.QueryRowContext(ctx,
+		`SELECT id FROM calendar_accounts WHERE user_id = ? AND provider = ?`,
+		a.UserID, a.Provider).Scan(&a.ID)
+}
+
+// MarkCalendarSynced records how far a run got. Written separately from the rest
+// so a sync never rewrites the credentials it is holding in memory.
+func (db *DB) MarkCalendarSynced(ctx context.Context, accountID string, at time.Time) error {
+	_, err := db.ExecContext(ctx,
+		`UPDATE calendar_accounts SET last_sync_at = ? WHERE id = ?`, at.Unix(), accountID)
+	return err
+}
+
+// DeleteCalendarAccount disconnects one. The calendars and their events go with it
+// — unlike the tasks a mailbox made, none of this is the person's own work; it is
+// a copy of somebody else's calendar and it has no meaning without the account.
+func (db *DB) DeleteCalendarAccount(ctx context.Context, userID, id string) error {
+	_, err := db.ExecContext(ctx,
+		`DELETE FROM calendar_accounts WHERE id = ? AND user_id = ?`, id, userID)
+	return err
+}
+
+// UsersWithCalendars returns everybody the sweep has to visit.
+func (db *DB) UsersWithCalendars(ctx context.Context) ([]string, error) {
+	rows, err := db.QueryContext(ctx, `SELECT DISTINCT user_id FROM calendar_accounts`)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+
+	var ids []string
+	for rows.Next() {
+		var id string
+		if err := rows.Scan(&id); err != nil {
+			return nil, err
+		}
+		ids = append(ids, id)
+	}
+	return ids, rows.Err()
+}
+
+// Calendars returns what one account holds, in the order the provider listed them.
+func (db *DB) Calendars(ctx context.Context, accountID string) ([]Calendar, error) {
+	rows, err := db.QueryContext(ctx, `
+		SELECT id, account_id, remote_id, name, colour, time_zone, primary_one,
+		       writable, shown, sort_order
+		FROM calendars WHERE account_id = ? ORDER BY sort_order, name`, accountID)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+
+	var out []Calendar
+	for rows.Next() {
+		var c Calendar
+		if err := rows.Scan(&c.ID, &c.AccountID, &c.RemoteID, &c.Name, &c.Colour,
+			&c.TimeZone, &c.Primary, &c.Writable, &c.Shown, &c.SortOrder); err != nil {
+			return nil, err
+		}
+		out = append(out, c)
+	}
+	return out, rows.Err()
+}
+
+// ReplaceCalendars writes the list the provider just gave, keeping what the person
+// chose.
+//
+// The choice survives because it is not in the list: Google says which calendars
+// exist and what they are called, and only verdande knows which of them somebody
+// wants to look at. Merged rather than deleted and rewritten, so ticking a calendar
+// on does not come undone the next time the sweep runs.
+//
+// A calendar that has disappeared from the account is removed, and its events go
+// with it — a calendar somebody was unshared from should stop being drawn, not
+// stay behind as a frozen copy of what it held on the last good day.
+func (db *DB) ReplaceCalendars(ctx context.Context, accountID string, list []Calendar) error {
+	return db.Tx(ctx, func(tx *sql.Tx) error {
+		keep := map[string]bool{}
+		for i, c := range list {
+			keep[c.RemoteID] = true
+			// The insert cannot carry `shown`: on conflict it would overwrite the
+			// choice with the default. A new calendar starts hidden — an account
+			// with a dozen shared calendars in it should not fill somebody's grid
+			// the moment they connect it.
+			if _, err := tx.ExecContext(ctx, `
+				INSERT INTO calendars
+				    (id, account_id, remote_id, name, colour, time_zone, primary_one,
+				     writable, shown, sort_order)
+				VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
+				ON CONFLICT (account_id, remote_id) DO UPDATE SET
+				    name = excluded.name,
+				    colour = excluded.colour,
+				    time_zone = excluded.time_zone,
+				    primary_one = excluded.primary_one,
+				    writable = excluded.writable,
+				    sort_order = excluded.sort_order`,
+				NewID(), accountID, c.RemoteID, c.Name, c.Colour, c.TimeZone,
+				c.Primary, c.Writable, c.Shown, i); err != nil {
+				return err
+			}
+		}
+
+		rows, err := tx.QueryContext(ctx,
+			`SELECT id, remote_id FROM calendars WHERE account_id = ?`, accountID)
+		if err != nil {
+			return err
+		}
+		var gone []string
+		for rows.Next() {
+			var id, remote string
+			if err := rows.Scan(&id, &remote); err != nil {
+				rows.Close()
+				return err
+			}
+			if !keep[remote] {
+				gone = append(gone, id)
+			}
+		}
+		// Closed before the next statement runs on this transaction. An open result
+		// set with a query behind it is the deadlock the pool comment in store.go
+		// exists to make slow rather than fatal.
+		rows.Close()
+		if err := rows.Err(); err != nil {
+			return err
+		}
+
+		for _, id := range gone {
+			if _, err := tx.ExecContext(ctx, `DELETE FROM calendars WHERE id = ?`, id); err != nil {
+				return err
+			}
+		}
+		return nil
+	})
+}
+
+// ShowCalendars sets which of an account's calendars are drawn.
+//
+// The whole set in one write rather than one flip at a time, for the reason the
+// projects' order is written the same way: a person has a handful of calendars, the
+// question is "these ones", and a list that can only be built by several requests
+// can land half applied.
+func (db *DB) ShowCalendars(ctx context.Context, accountID string, shown []string) error {
+	return db.Tx(ctx, func(tx *sql.Tx) error {
+		if _, err := tx.ExecContext(ctx,
+			`UPDATE calendars SET shown = 0 WHERE account_id = ?`, accountID); err != nil {
+			return err
+		}
+		for _, id := range shown {
+			// Scoped in the SQL rather than checked first: an id read in one step
+			// and written in the next is a window, and the account is the whole of
+			// the permission here.
+			if _, err := tx.ExecContext(ctx,
+				`UPDATE calendars SET shown = 1 WHERE id = ? AND account_id = ?`,
+				id, accountID); err != nil {
+				return err
+			}
+		}
+		// Events of a calendar nobody is looking at are dead weight in a table the
+		// grid queries. They come back with the next sync if it is turned on again.
+		_, err := tx.ExecContext(ctx, `
+			DELETE FROM calendar_events WHERE calendar_id IN
+			    (SELECT id FROM calendars WHERE account_id = ? AND shown = 0)`, accountID)
+		return err
+	})
+}
+
+// ReplaceCalendarEvents swaps one calendar's events inside a window.
+//
+// Replaced rather than merged, and no sync token. Google offers incremental sync,
+// and it would save bytes verdande is not short of while costing the one thing it
+// cannot afford: a token that has to be right, forever, for the grid not to be
+// quietly wrong. A window that is deleted and rewritten cannot drift — an event
+// somebody moved out of the window disappears because it is not in the answer, not
+// because verdande remembered to delete it.
+//
+// Bounded by the window at both ends, so a sync of September does not throw away
+// August.
+func (db *DB) ReplaceCalendarEvents(ctx context.Context, calendarID, from, to string, events []CalendarEvent) error {
+	return db.Tx(ctx, func(tx *sql.Tx) error {
+		if _, err := tx.ExecContext(ctx, `
+			DELETE FROM calendar_events
+			WHERE calendar_id = ? AND end_day >= ? AND start_day <= ?`,
+			calendarID, from, to); err != nil {
+			return err
+		}
+		for _, e := range events {
+			if _, err := tx.ExecContext(ctx, `
+				INSERT INTO calendar_events
+				    (id, calendar_id, remote_id, summary, starts_at, ends_at,
+				     start_day, end_day, all_day, location, url)
+				VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)`,
+				NewID(), calendarID, e.RemoteID, e.Summary, e.StartsAt, e.EndsAt,
+				e.StartDay, e.EndDay, e.AllDay, e.Location, e.URL); err != nil {
+				return err
+			}
+		}
+		return nil
+	})
+}
+
+// CalendarEvents returns everything one person can see between two days,
+// inclusive at both ends.
+//
+// Scoped to the caller in the join rather than checked afterwards: the events of
+// somebody else's calendar are somebody else's, and a filter applied after the read
+// is a filter that can be forgotten.
+func (db *DB) CalendarEvents(ctx context.Context, userID, from, to string) ([]CalendarEvent, error) {
+	rows, err := db.QueryContext(ctx, `
+		SELECT e.id, e.calendar_id, e.remote_id, e.summary, e.starts_at, e.ends_at,
+		       e.start_day, e.end_day, e.all_day, e.location, e.url, c.name, c.colour
+		FROM calendar_events e
+		JOIN calendars c ON c.id = e.calendar_id
+		JOIN calendar_accounts a ON a.id = c.account_id
+		WHERE a.user_id = ? AND c.shown = 1 AND e.end_day >= ? AND e.start_day <= ?
+		ORDER BY e.start_day, e.all_day DESC, e.starts_at`, userID, from, to)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+
+	var out []CalendarEvent
+	for rows.Next() {
+		var e CalendarEvent
+		if err := rows.Scan(&e.ID, &e.CalendarID, &e.RemoteID, &e.Summary, &e.StartsAt,
+			&e.EndsAt, &e.StartDay, &e.EndDay, &e.AllDay, &e.Location, &e.URL,
+			&e.CalendarName, &e.Colour); err != nil {
+			return nil, err
+		}
+		out = append(out, e)
+	}
+	return out, rows.Err()
+}
+
+func (db *DB) scanCalendarAccount(row scanner) (CalendarAccount, error) {
+	var a CalendarAccount
+	var expires, lastSync, created int64
+	err := row.Scan(&a.ID, &a.UserID, &a.Provider, &a.Account, &a.RefreshToken,
+		&a.AccessToken, &expires, &lastSync, &created)
+	if err != nil {
+		return a, err
+	}
+	for _, field := range []*string{&a.RefreshToken, &a.AccessToken} {
+		plain, err := db.unsealValue(*field)
+		if err != nil {
+			return a, err
+		}
+		*field = plain
+	}
+	a.ExpiresAt = timeOrZero(expires)
+	a.LastSyncAt = timeOrZero(lastSync)
+	a.CreatedAt = time.Unix(created, 0)
+	return a, nil
+}
@@ -0,0 +1,358 @@
+package store
+
+import (
+	"context"
+	"strings"
+	"testing"
+	"time"
+)
+
+func connectedAccount(t *testing.T, db *DB, userID string) *CalendarAccount {
+	t.Helper()
+	a := &CalendarAccount{
+		UserID: userID, Provider: "google", Account: "[email protected]",
+		RefreshToken: "1//0-a-real-looking-refresh-token", AccessToken: "ya29.access",
+		ExpiresAt: time.Now().Add(time.Hour),
+	}
+	if err := db.SaveCalendarAccount(context.Background(), a); err != nil {
+		t.Fatal(err)
+	}
+	return a
+}
+
+// The same claim the mailbox tokens have to meet: what is written must not be
+// readable in the file a backup copies.
+func TestCalendarTokensAreNotStoredInTheClear(t *testing.T) {
+	db, userID := sealedStore(t)
+	ctx := context.Background()
+	a := connectedAccount(t, db, userID)
+
+	var refresh, access string
+	if err := db.QueryRowContext(ctx,
+		`SELECT refresh_token, access_token FROM calendar_accounts WHERE id = ?`,
+		a.ID).Scan(&refresh, &access); err != nil {
+		t.Fatal(err)
+	}
+	if strings.Contains(refresh, "real-looking") || strings.Contains(access, "ya29") {
+		t.Fatalf("a token is in the row as written: %q %q", refresh, access)
+	}
+	// The address stays readable, which is the reason for sealing named columns
+	// rather than the whole row.
+	var account string
+	if err := db.QueryRowContext(ctx,
+		`SELECT account FROM calendar_accounts WHERE id = ?`, a.ID).Scan(&account); err != nil {
+		t.Fatal(err)
+	}
+	if account != "[email protected]" {
+		t.Errorf("the address was sealed too: %q", account)
+	}
+
+	back, err := db.CalendarAccountFor(ctx, userID, "google")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if back.RefreshToken != a.RefreshToken || back.AccessToken != a.AccessToken {
+		t.Errorf("the tokens did not survive the round trip: %+v", back)
+	}
+}
+
+// Connecting again must replace what was there, not fail. It is the same OAuth
+// flow run a second time, and the person's word for it is "connect", not "add".
+func TestConnectingAgainReplacesTheAccount(t *testing.T) {
+	db, userID := sealedStore(t)
+	ctx := context.Background()
+	first := connectedAccount(t, db, userID)
+
+	second := &CalendarAccount{
+		UserID: userID, Provider: "google", Account: "[email protected]",
+		RefreshToken: "1//0-fresh", AccessToken: "ya29.fresh",
+	}
+	if err := db.SaveCalendarAccount(ctx, second); err != nil {
+		t.Fatalf("connecting a second time failed: %v", err)
+	}
+	// And the id in hand is the row that is actually there. The calendars hang off
+	// it, so an id nothing points at would attach them to nothing.
+	if second.ID != first.ID {
+		t.Errorf("the second connect came back with id %q, want the existing %q",
+			second.ID, first.ID)
+	}
+
+	back, err := db.CalendarAccountFor(ctx, userID, "google")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if back.RefreshToken != "1//0-fresh" {
+		t.Errorf("the token came back as %q", back.RefreshToken)
+	}
+}
+
+// Google says which calendars exist; only verdande knows which ones somebody wants
+// to look at. A refresh that came back with the same list must not undo the choice.
+func TestRefreshingTheListKeepsWhatWasChosen(t *testing.T) {
+	db, userID := sealedStore(t)
+	ctx := context.Background()
+	a := connectedAccount(t, db, userID)
+
+	list := []Calendar{
+		{RemoteID: "primary", Name: "[email protected]", Colour: "#3f51b5", Primary: true},
+		{RemoteID: "fam", Name: "Familien", Colour: "#0b8043"},
+		{RemoteID: "old", Name: "Et delt"},
+	}
+	if err := db.ReplaceCalendars(ctx, a.ID, list); err != nil {
+		t.Fatal(err)
+	}
+
+	// Nothing is shown to begin with: an account with a dozen shared calendars in
+	// it should not fill somebody's grid the moment they connect it.
+	stored, err := db.Calendars(ctx, a.ID)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(stored) != 3 {
+		t.Fatalf("got %d calendars, want 3", len(stored))
+	}
+	for _, c := range stored {
+		if c.Shown {
+			t.Errorf("%q was shown without anybody asking for it", c.Name)
+		}
+	}
+
+	var famID string
+	for _, c := range stored {
+		if c.RemoteID == "fam" {
+			famID = c.ID
+		}
+	}
+	if err := db.ShowCalendars(ctx, a.ID, []string{famID}); err != nil {
+		t.Fatal(err)
+	}
+
+	// The sweep runs again, and one calendar has been renamed and one has gone.
+	if err := db.ReplaceCalendars(ctx, a.ID, []Calendar{
+		{RemoteID: "primary", Name: "[email protected]", Colour: "#3f51b5", Primary: true},
+		{RemoteID: "fam", Name: "Familien og hunden", Colour: "#0b8043"},
+	}); err != nil {
+		t.Fatal(err)
+	}
+
+	stored, err = db.Calendars(ctx, a.ID)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(stored) != 2 {
+		t.Fatalf("got %d calendars; one that has left the account should stop being drawn",
+			len(stored))
+	}
+	for _, c := range stored {
+		switch c.RemoteID {
+		case "fam":
+			if !c.Shown {
+				t.Error("the choice was undone by a refresh of the list")
+			}
+			if c.Name != "Familien og hunden" {
+				t.Errorf("the new name did not arrive: %q", c.Name)
+			}
+			if c.ID != famID {
+				t.Error("the row was rebuilt rather than updated; its id is what was chosen")
+			}
+		case "primary":
+			if c.Shown {
+				t.Error("a calendar nobody chose became shown")
+			}
+		}
+	}
+}
+
+// A window is replaced, not merged. An event moved out of it has to disappear
+// because it is absent from the answer — and the months on either side must not go
+// with it.
+func TestReplacingAWindowLeavesTheMonthsAroundItAlone(t *testing.T) {
+	db, userID := sealedStore(t)
+	ctx := context.Background()
+	a := connectedAccount(t, db, userID)
+
+	if err := db.ReplaceCalendars(ctx, a.ID, []Calendar{{RemoteID: "primary", Name: "Min"}}); err != nil {
+		t.Fatal(err)
+	}
+	stored, _ := db.Calendars(ctx, a.ID)
+	cal := stored[0]
+	if err := db.ShowCalendars(ctx, a.ID, []string{cal.ID}); err != nil {
+		t.Fatal(err)
+	}
+
+	july := CalendarEvent{RemoteID: "j", Summary: "Juli", StartDay: "2026-07-15", EndDay: "2026-07-15"}
+	august := CalendarEvent{RemoteID: "a", Summary: "August", StartDay: "2026-08-15", EndDay: "2026-08-15"}
+	if err := db.ReplaceCalendarEvents(ctx, cal.ID, "2026-07-01", "2026-07-31",
+		[]CalendarEvent{july}); err != nil {
+		t.Fatal(err)
+	}
+	if err := db.ReplaceCalendarEvents(ctx, cal.ID, "2026-08-01", "2026-08-31",
+		[]CalendarEvent{august}); err != nil {
+		t.Fatal(err)
+	}
+
+	got, err := db.CalendarEvents(ctx, userID, "2026-07-01", "2026-08-31")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(got) != 2 {
+		t.Fatalf("got %d events, want both months: %+v", len(got), got)
+	}
+
+	// August is synced again and the meeting has been cancelled. July stays.
+	if err := db.ReplaceCalendarEvents(ctx, cal.ID, "2026-08-01", "2026-08-31", nil); err != nil {
+		t.Fatal(err)
+	}
+	got, err = db.CalendarEvents(ctx, userID, "2026-07-01", "2026-08-31")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(got) != 1 || got[0].Summary != "Juli" {
+		t.Fatalf("got %+v; syncing August threw away July", got)
+	}
+}
+
+// The grid asks "which cells does this cover", so an event that straddles the edge
+// of the question has to come back.
+func TestAnEventThatStraddlesTheWindowIsFound(t *testing.T) {
+	db, userID := sealedStore(t)
+	ctx := context.Background()
+	a := connectedAccount(t, db, userID)
+	if err := db.ReplaceCalendars(ctx, a.ID, []Calendar{{RemoteID: "c", Name: "Min", Colour: "#0b8043"}}); err != nil {
+		t.Fatal(err)
+	}
+	stored, _ := db.Calendars(ctx, a.ID)
+	if err := db.ShowCalendars(ctx, a.ID, []string{stored[0].ID}); err != nil {
+		t.Fatal(err)
+	}
+	if err := db.ReplaceCalendarEvents(ctx, stored[0].ID, "2026-08-01", "2026-09-30",
+		[]CalendarEvent{
+			{RemoteID: "trip", Summary: "Aarhus", StartDay: "2026-08-28", EndDay: "2026-09-02", AllDay: true},
+		}); err != nil {
+		t.Fatal(err)
+	}
+
+	// A week that contains neither end of it.
+	got, err := db.CalendarEvents(ctx, userID, "2026-08-31", "2026-09-01")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(got) != 1 {
+		t.Fatalf("got %+v; an event covering the whole week was not found", got)
+	}
+	// The calendar's own colour rides along, or the chip has to ask for it per row.
+	if got[0].Colour != "#0b8043" || got[0].CalendarName != "Min" {
+		t.Errorf("the calendar did not come with the event: %+v", got[0])
+	}
+}
+
+// Somebody else's calendar is somebody else's.
+func TestOnlyTheOwnersEventsComeBack(t *testing.T) {
+	db, userID := sealedStore(t)
+	ctx := context.Background()
+
+	other := &User{Email: "[email protected]", Name: "Andreas"}
+	if err := db.CreateUser(ctx, other, "Indbakke"); err != nil {
+		t.Fatal(err)
+	}
+	theirs := &CalendarAccount{UserID: other.ID, Provider: "google", RefreshToken: "r"}
+	if err := db.SaveCalendarAccount(ctx, theirs); err != nil {
+		t.Fatal(err)
+	}
+	if err := db.ReplaceCalendars(ctx, theirs.ID, []Calendar{{RemoteID: "c", Name: "Deres"}}); err != nil {
+		t.Fatal(err)
+	}
+	stored, _ := db.Calendars(ctx, theirs.ID)
+	if err := db.ShowCalendars(ctx, theirs.ID, []string{stored[0].ID}); err != nil {
+		t.Fatal(err)
+	}
+	if err := db.ReplaceCalendarEvents(ctx, stored[0].ID, "2026-08-01", "2026-08-31",
+		[]CalendarEvent{{RemoteID: "x", Summary: "Privat", StartDay: "2026-08-10", EndDay: "2026-08-10"}}); err != nil {
+		t.Fatal(err)
+	}
+
+	got, err := db.CalendarEvents(ctx, userID, "2026-08-01", "2026-08-31")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(got) != 0 {
+		t.Fatalf("somebody else's calendar came back: %+v", got)
+	}
+}
+
+// A calendar turned off stops being drawn, and stops costing the grid anything.
+func TestTurningACalendarOffRemovesItsEvents(t *testing.T) {
+	db, userID := sealedStore(t)
+	ctx := context.Background()
+	a := connectedAccount(t, db, userID)
+	if err := db.ReplaceCalendars(ctx, a.ID, []Calendar{{RemoteID: "c", Name: "Min"}}); err != nil {
+		t.Fatal(err)
+	}
+	stored, _ := db.Calendars(ctx, a.ID)
+	if err := db.ShowCalendars(ctx, a.ID, []string{stored[0].ID}); err != nil {
+		t.Fatal(err)
+	}
+	if err := db.ReplaceCalendarEvents(ctx, stored[0].ID, "2026-08-01", "2026-08-31",
+		[]CalendarEvent{{RemoteID: "x", Summary: "Møde", StartDay: "2026-08-10", EndDay: "2026-08-10"}}); err != nil {
+		t.Fatal(err)
+	}
+
+	if err := db.ShowCalendars(ctx, a.ID, nil); err != nil {
+		t.Fatal(err)
+	}
+	var count int
+	if err := db.QueryRowContext(ctx, `SELECT count(*) FROM calendar_events`).Scan(&count); err != nil {
+		t.Fatal(err)
+	}
+	if count != 0 {
+		t.Errorf("%d events of a calendar nobody is looking at are still in the table", count)
+	}
+}
+
+// Disconnecting takes the calendars and the events with it. Unlike the tasks a
+// mailbox made, none of this is the person's own work — it is a copy of somebody
+// else's calendar and it means nothing without the account.
+func TestDisconnectingTakesEverythingWithIt(t *testing.T) {
+	db, userID := sealedStore(t)
+	ctx := context.Background()
+	a := connectedAccount(t, db, userID)
+	if err := db.ReplaceCalendars(ctx, a.ID, []Calendar{{RemoteID: "c", Name: "Min"}}); err != nil {
+		t.Fatal(err)
+	}
+	stored, _ := db.Calendars(ctx, a.ID)
+	if err := db.ShowCalendars(ctx, a.ID, []string{stored[0].ID}); err != nil {
+		t.Fatal(err)
+	}
+	if err := db.ReplaceCalendarEvents(ctx, stored[0].ID, "2026-08-01", "2026-08-31",
+		[]CalendarEvent{{RemoteID: "x", Summary: "Møde", StartDay: "2026-08-10", EndDay: "2026-08-10"}}); err != nil {
+		t.Fatal(err)
+	}
+
+	if err := db.DeleteCalendarAccount(ctx, userID, a.ID); err != nil {
+		t.Fatal(err)
+	}
+	for _, table := range []string{"calendar_accounts", "calendars", "calendar_events"} {
+		var count int
+		if err := db.QueryRowContext(ctx, `SELECT count(*) FROM `+table).Scan(&count); err != nil {
+			t.Fatal(err)
+		}
+		if count != 0 {
+			t.Errorf("%s still holds %d rows after disconnecting", table, count)
+		}
+	}
+}
+
+// The sweep finds people by the presence of an account, so it has to keep working
+// now that the credential in it is ciphertext.
+func TestTheSweepFindsAConnectedCalendar(t *testing.T) {
+	db, userID := sealedStore(t)
+	connectedAccount(t, db, userID)
+
+	users, err := db.UsersWithCalendars(context.Background())
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(users) != 1 || users[0] != userID {
+		t.Fatalf("the sweep found %v", users)
+	}
+}
@@ -0,0 +1,111 @@
+-- Calendars read from somewhere else: the account, the calendars in it, and the
+-- events they hold.
+--
+-- Not in `mailboxes`, and it was the first thing considered. The two look alike
+-- from a distance — a person connects a Google account over OAuth, tokens are
+-- sealed, a sweep polls it — and every column past that disagrees. `trigger_kind`,
+-- `seen`, `last_uid` and `project_id` all answer "what turns a message into a
+-- task", and nothing here turns into a task. What is here instead is a *set*:
+-- one account holds many calendars, and a person picks which of them to look at.
+-- `mailboxes` has no room for a one-to-many, and giving it one would push the
+-- other kind's columns onto rows that can never use them.
+--
+-- The decisive part is smaller and more practical. `mailboxes.kind` carries
+-- `CHECK (kind IN ('gmail', 'imap'))`, and SQLite cannot alter a CHECK — adding a
+-- third value means rebuilding the table with foreign keys off, which is the
+-- expensive, careful thing migration 0021 had to do for a reason. Paying that to
+-- store something that shares no column with the table is the wrong trade.
+--
+-- Hence no CHECK on `provider` here. CalDAV is the next source to read, and it
+-- should cost a row, not a rebuild.
+
+-- One connected account per person per provider. The tokens live here rather than
+-- on each calendar: a refresh token copied onto ten rows is ten copies of one
+-- secret, ten refreshes racing each other, and ten places to miss when access is
+-- revoked.
+--
+-- `refresh_token` and `access_token` are written sealed; see internal/secret. The
+-- store's own seal/unseal only covers the settings tables, so this table's methods
+-- call them by hand — the same fact worth knowing that migration 0014 wrote down.
+CREATE TABLE calendar_accounts (
+    id            TEXT PRIMARY KEY,
+    user_id       TEXT NOT NULL REFERENCES users (id) ON DELETE CASCADE,
+    provider      TEXT NOT NULL DEFAULT 'google',
+    -- The address the account reports, so the settings page can say which one is
+    -- connected rather than only that one is.
+    account       TEXT NOT NULL DEFAULT '',
+
+    refresh_token TEXT NOT NULL DEFAULT '',
+    access_token  TEXT NOT NULL DEFAULT '',
+    expires_at    INTEGER NOT NULL DEFAULT 0,
+
+    last_sync_at  INTEGER NOT NULL DEFAULT 0,
+    created_at    INTEGER NOT NULL
+);
+
+-- Connecting again replaces what was there, the way Gmail's does: the OAuth flow
+-- is one account at a time, so a second row for the same provider would be a
+-- second set of tokens for the same grant and no way to say which is live.
+CREATE UNIQUE INDEX calendar_accounts_once ON calendar_accounts (user_id, provider);
+
+-- One row per calendar the account can see, kept whether or not it is shown.
+--
+-- `shown` rather than deleting the ones that are not: a person who turns a calendar
+-- off and on again should get the same row back, and the list is refreshed from
+-- Google on every sync — so a calendar that only existed while it was ticked would
+-- lose its choice every time somebody added a new one.
+--
+-- `colour` is Google's own hex for the calendar. Not one of verdande's ten named
+-- colours, which is the rule everywhere else in this database: those are names so
+-- the interface can restyle them per theme, and they are *verdande's* palette. A
+-- Google calendar is told apart by the colour the person already knows it by, and
+-- that colour belongs to Google.
+CREATE TABLE calendars (
+    id         TEXT PRIMARY KEY,
+    account_id TEXT NOT NULL REFERENCES calendar_accounts (id) ON DELETE CASCADE,
+    -- The id Google knows it by. Long, and an address for the primary calendar.
+    remote_id  TEXT NOT NULL,
+    name       TEXT NOT NULL DEFAULT '',
+    colour     TEXT NOT NULL DEFAULT '',
+    time_zone  TEXT NOT NULL DEFAULT '',
+    primary_one INTEGER NOT NULL DEFAULT 0,
+    writable   INTEGER NOT NULL DEFAULT 0,
+    shown      INTEGER NOT NULL DEFAULT 0,
+    sort_order INTEGER NOT NULL DEFAULT 0
+);
+
+CREATE UNIQUE INDEX calendars_once ON calendars (account_id, remote_id);
+
+-- The events themselves, cached.
+--
+-- Cached rather than fetched per view, and the reason is what a month grid does:
+-- it pages. Asking Google on every arrow press means a token refresh, a round trip
+-- and a spinner for a question that was answered ninety seconds ago — and a
+-- calendar that is slower than the calendar it is showing is not worth having.
+-- The window is refreshed by the sweep and by the "fetch now" button.
+--
+-- Days rather than instants, and both ends inclusive. A grid asks one question —
+-- "which cells does this cover" — and `start_day <= ? AND end_day >= ?` is that
+-- question. `starts_at` is kept as Google wrote it, offset and all, because it is
+-- what the chip shows and reparsing it here would ask *this process* what time
+-- zone it is in. An all-day event has neither: it has a day, not a moment, and
+-- inventing midnight for it is how an event moves a day when a container moves
+-- time zone.
+CREATE TABLE calendar_events (
+    id          TEXT PRIMARY KEY,
+    calendar_id TEXT NOT NULL REFERENCES calendars (id) ON DELETE CASCADE,
+    remote_id   TEXT NOT NULL,
+    summary     TEXT NOT NULL DEFAULT '',
+    starts_at   TEXT NOT NULL DEFAULT '',
+    ends_at     TEXT NOT NULL DEFAULT '',
+    start_day   TEXT NOT NULL,
+    end_day     TEXT NOT NULL,
+    all_day     INTEGER NOT NULL DEFAULT 0,
+    location    TEXT NOT NULL DEFAULT '',
+    url         TEXT NOT NULL DEFAULT ''
+);
+
+-- The one query there is: everything a person can see, between two days. Ordered
+-- by the account so the join has somewhere to start, then by the days the grid
+-- compares against.
+CREATE INDEX calendar_events_by_day ON calendar_events (calendar_id, start_day, end_day);
@@ -979,6 +979,211 @@ test('en opgave kan trækkes hen over et månedsskifte i uge-visningen', async (
 * asserting against a project the admin can already see would pass with the old
 * per-project endpoint behind it.
 */
+/**
+ * Kalender: Google's events and verdande's own tasks in one grid, and the rule
+ * that tells them apart.
+ *
+ * The Google half is stubbed at the network layer rather than connected. There are
+ * no credentials in a test run and there never will be — an OAuth consent screen is
+ * a human pressing a button on somebody else's website — so what can be proved here
+ * is what the grid does with events once it has them, which is the part that has a
+ * rule in it: a task is draggable and reschedules, an event is not and cannot.
+ *
+ * The date is read out of the *page*, not out of this process. Playwright pins the
+ * browser to Europe/Copenhagen and node is pinned to nothing, so for two hours of
+ * every day the two disagree about what today is — which is how a green suite
+ * starts failing at half past midnight. Today is also the one day guaranteed to be
+ * in the month grid whatever the weekday, so nothing here has to page.
+ */
+test('kalenderen viser Googles begivenheder over egne opgaver, og kun opgaven kan trækkes', async ({
+	page
+}) => {
+	const trouble = watchForTrouble(page);
+	await page.goto('/');
+
+	// A day at least a week out, whose next day is in the same Monday-to-Sunday
+	// week — so the drag below crosses one cell and not one grid.
+	//
+	// Worked out in the browser, not here. Playwright pins the page to
+	// Europe/Copenhagen and this process is pinned to nothing, so for two hours of
+	// every day the two disagree about what today is. A week out also keeps this
+	// test's day clear of the ones the rest of the suite dates things on.
+	const { day, next } = await page.evaluate(() => {
+		const iso = (d) =>
+			`${d.getFullYear()}-${String(d.getMonth() + 1).padStart(2, '0')}-${String(
+				d.getDate()
+			).padStart(2, '0')}`;
+		const monday = (d) => {
+			const m = new Date(d.getFullYear(), d.getMonth(), d.getDate());
+			m.setDate(m.getDate() - ((m.getDay() + 6) % 7));
+			return iso(m);
+		};
+		const cursor = new Date();
+		cursor.setDate(cursor.getDate() + 7);
+		for (let i = 0; i < 14; i++) {
+			cursor.setDate(cursor.getDate() + 1);
+			const after = new Date(cursor.getFullYear(), cursor.getMonth(), cursor.getDate() + 1);
+			if (monday(cursor) === monday(after)) return { day: iso(cursor), next: iso(after) };
+		}
+		throw new Error('no two consecutive days inside one week in three weeks');
+	});
+
+	// A calendar that is connected and holds two events that day: one with a clock
+	// and one that lasts the whole day. The window is deliberately wide, so the
+	// notice about having paged past it stays out of the way.
+	await page.route('**/api/v1/calendar/events*', (route) =>
+		route.fulfill({
+			json: {
+				from: '2000-01-01',
+				to: '2099-12-31',
+				events: [
+					{
+						id: 'ev-1',
+						calendar_id: 'c1',
+						summary: 'Bestyrelsesmøde',
+						starts_at: `${day}T14:00:00+02:00`,
+						ends_at: `${day}T15:30:00+02:00`,
+						start_day: day,
+						end_day: day,
+						all_day: false,
+						url: 'https://calendar.google.com/event?eid=abc',
+						calendar_name: 'Arbejde',
+						colour: '#0b8043'
+					},
+					{
+						id: 'ev-2',
+						calendar_id: 'c1',
+						summary: 'Feriedag',
+						start_day: day,
+						end_day: day,
+						all_day: true,
+						calendar_name: 'Familien',
+						colour: '#3f51b5'
+					}
+				]
+			}
+		})
+	);
+	await page.route('**/api/v1/calendar', (route) =>
+		route.fulfill({
+			json: {
+				connected: true,
+				account: '[email protected]',
+				read_only: true,
+				has_client: true,
+				redirect_uri: 'http://localhost/oauth/calendar/callback',
+				calendars: [
+					{ id: 'c1', remote_id: 'fam', name: 'Arbejde', colour: '#0b8043', shown: true }
+				]
+			}
+		})
+	);
+
+	// verdande's own half of the grid: a task on that day, made the way anybody
+	// would make it. The date is written out rather than typed as "i morgen", so
+	// the assertion does not depend on the parser as well.
+	const box = page.getByLabel('Ny opgave');
+	await box.fill(`vande blomster ${day}`);
+	await box.press('Enter');
+	// Not asserted here: this is the Today view and the task is dated a week out,
+	// so it is correctly absent. The grid below is where it has to turn up.
+	await expect(box).toHaveValue('');
+
+	// The menu item, which is the thing the sidebar gained.
+	const sidebar = page.getByRole('navigation', { name: 'Hovedmenu' });
+	await sidebar.locator('a[href="/kalender"]').click();
+	await page.waitForURL('**/kalender');
+	await expect(page.getByRole('heading', { name: 'Kalender', level: 1 })).toBeVisible();
+
+	// The week, not the month, and for a reason worth writing down: a month cell
+	// truncates at three chips and this suite has other tests putting tasks on
+	// other days. A week cell holds ten, so what is asserted below is what the view
+	// does with events rather than how full somebody else left the month.
+	await page.getByRole('button', { name: 'Uge', exact: true }).click();
+
+	// Forward a week at a time until the row is the one holding that day. Bounded,
+	// because a loop that pages for ever on a broken button is a timeout with no
+	// explanation in it.
+	const cell = page.locator(`[data-date="${day}"]`);
+	const forward = page.getByRole('button', { name: 'Næste uge' });
+	for (let i = 0; i < 6 && (await cell.count()) === 0; i++) {
+		await forward.click();
+	}
+	await expect(cell, `uge-visningen nåede aldrig frem til ${day}`).toBeVisible();
+
+	// Connected, with a calendar ticked — so neither of the two "there is nothing
+	// here" notices belongs on the screen. They exist so an empty grid is never
+	// unexplained, and an explanation for a state you are not in is noise.
+	await expect(page.getByText('Ingen kalender er forbundet endnu.')).toBeHidden();
+	await expect(page.getByText('Ingen af kontoens kalendere er valgt endnu.')).toBeHidden();
+
+	// Both kinds are in the same cell, which is the whole point of the view.
+	const event = cell.locator('.event').filter({ hasText: 'Bestyrelsesmøde' });
+	const allDay = cell.locator('.event').filter({ hasText: 'Feriedag' });
+	const task = cell.locator('.chip').filter({ hasText: 'vande blomster' });
+	await expect(event).toBeVisible();
+	await expect(allDay).toBeVisible();
+	await expect(task).toBeVisible();
+
+	// A timed event carries its clock; an all-day one has none to carry.
+	await expect(event).toContainText('14:00');
+	await expect(allDay).not.toContainText(':');
+
+	// The rule. An event is read-only, so it must not offer to be moved — the drop
+	// targets would refuse it anyway, but a chip that lifts off the page and then
+	// will not land reads as a bug rather than as a rule.
+	await expect(event).toHaveAttribute('draggable', 'false');
+	await expect(allDay).toHaveAttribute('draggable', 'false');
+	await expect(task).toHaveAttribute('draggable', 'true');
+
+	// And it cannot be ticked off either: there is nothing to complete about
+	// somebody else's meeting.
+	expect(await event.evaluate((el) => el.tagName)).not.toBe('BUTTON');
+
+	// It does link back to Google, which is what makes it a pointer to the event
+	// rather than a second copy of it.
+	await expect(event).toHaveAttribute('href', /^https:\/\/calendar\.google\.com\//);
+
+	// The task still reschedules by drag, in a grid that now has events in it.
+	await task.dragTo(page.locator(`[data-date="${next}"]`));
+	await expect(page.locator(`[data-date="${next}"]`).getByText('vande blomster')).toBeVisible();
+	await expect(cell.getByText('vande blomster')).toBeHidden();
+	// The events stayed where they were; a rescheduled task moves nothing else.
+	await expect(cell.locator('.event')).toHaveCount(2);
+
+	expect(trouble).toEqual([]);
+});
+
+/**
+ * The view without a calendar connected, which is what every fresh instance is.
+ *
+ * It has to draw anyway. The grid is verdande's own tasks with due dates — the
+ * thing this view was before anything was laid over it — and a Google account that
+ * is not there must not take it down with it.
+ */
+test('kalenderen virker uden en forbundet Google-konto', async ({ page }) => {
+	const trouble = watchForTrouble(page);
+	await page.goto('/kalender');
+
+	await expect(page.getByRole('heading', { name: 'Kalender', level: 1 })).toBeVisible();
+	// Seven weekday columns and a grid under them, whatever day of the week it is.
+	await expect(page.locator('.calendar .grid .day').first()).toBeVisible();
+
+	// It says so rather than looking like a calendar with nothing in it, and it
+	// says where to go about it.
+	await expect(page.getByText('Ingen kalender er forbundet endnu.')).toBeVisible();
+	await expect(
+		page.locator('a[href="/indstillinger/integrationer"]').first()
+	).toBeVisible();
+
+	// The week is the same grid with a different span, and switching to it must not
+	// lose the events prop on the way.
+	await page.getByRole('button', { name: 'Uge', exact: true }).click();
+	await expect(page.locator('.calendar.week')).toBeVisible();
+
+	expect(trouble).toEqual([]);
+});
+
 test('historik-siden viser hændelser fra et projekt, administratoren ikke er med i', async ({
 	browser,
 	page
@@ -61,6 +61,10 @@ const MESSAGES = {
 	// Same shape for a mailbox read over IMAP: quoted when the host said something,
 	// this when it did not.
 	mailbox_failed: 'error.mailboxRefused',
+	// And for a calendar read from Google. Its own code, because the sentence this
+	// is wrapped in names where it came from — and "Gmail said no" about a calendar
+	// sends somebody to the wrong panel.
+	calendar_failed: 'error.calendarRefused',
 	last_admin: 'error.lastAdmin'
 };

@@ -84,6 +88,9 @@ export function humanMessage(err) {
 	if (err.code === 'gmail_failed' && err.message) {
 		return t('error.gmailSaid', { what: err.message });
 	}
+	if (err.code === 'calendar_failed' && err.message) {
+		return t('error.calendarSaid', { what: err.message });
+	}

 	const key = MESSAGES[err.code];
 	if (key) return t(key);
@@ -365,6 +372,16 @@ export const api = {
 	authorizeGmail: () => post('/gmail/authorize'),
 	syncGmail: () => post('/gmail/sync'),

+	// The Google Calendar connection. Read-only: there is nothing here that writes
+	// an event, only which calendars to look at.
+	getCalendar: () => get('/calendar'),
+	setCalendars: (shown) => put('/calendar/calendars', { shown }),
+	disconnectCalendar: () => del('/calendar'),
+	authorizeCalendar: () => post('/calendar/authorize'),
+	syncCalendar: () => post('/calendar/sync'),
+	calendarEvents: (from, to) =>
+		get(`/calendar/events?from=${encodeURIComponent(from)}&to=${encodeURIComponent(to)}`),
+
 	// Notes. Listing and searching are one endpoint because they answer the same
 	// question with different words.
 	notes: (params = {}) => {
@@ -49,7 +49,19 @@
 		 * flight swallows the click that would page. A week that straddles the
 		 * 31st and the 1st has both days in the same row.
 		 */
-		span = 'month'
+		span = 'month',
+		/**
+		 * Events read from somewhere else, laid over the same grid.
+		 *
+		 * An event is not a task, and the cell has to say so. It has a span of time
+		 * rather than a day, it cannot be ticked off, and — while the connection is
+		 * read-only — it cannot be moved: verdande holds a copy of somebody else's
+		 * calendar, and a chip that lets itself be dragged is a promise the server
+		 * has no way to keep.
+		 *
+		 * Empty everywhere but Kalender, so no other view pays for it.
+		 */
+		events = []
 	} = $props();

 	let cursor = $state(span === 'week' ? startOfWeek(new Date()) : startOfMonth(new Date()));
@@ -137,6 +149,66 @@
 				(!projectId || t.project_id === projectId)
 		);

+	/**
+	 * Which cells an event covers, rather than where it starts. A trip from Friday
+	 * to Monday is in all four, and asking only about the start day would draw it
+	 * once and leave three days looking clear.
+	 *
+	 * Ordered here rather than trusted from the caller. The server does sort, but a
+	 * cell that shows 14:00 above 09:15 does not look like a list in the wrong
+	 * order — it looks like the clock on the chip is wrong, which is a far worse
+	 * thing to have to rule out. All-day first, because an all-day event is a band
+	 * over the whole day rather than something that happens at a point in it.
+	 */
+	const eventsOn = (date) => {
+		const day = iso(date);
+		return events
+			.filter((e) => e.start_day <= day && e.end_day >= day)
+			.toSorted((a, b) => {
+				if (a.all_day !== b.all_day) return a.all_day ? -1 : 1;
+				return (a.starts_at ?? '').localeCompare(b.starts_at ?? '');
+			});
+	};
+
+	/**
+	 * The time on the chip, and only where it means something.
+	 *
+	 * An all-day event has no time. A timed one shows its start, and only on the
+	 * day it starts: a meeting that runs past midnight would otherwise claim to
+	 * begin at 20:00 on both days.
+	 *
+	 * The clock is read out of the string rather than parsed into a Date. Google
+	 * writes the event's own offset into it, and handing that to the browser asks
+	 * *this device* what time it is — so a phone in another time zone would show a
+	 * Copenhagen meeting an hour out.
+	 */
+	function timeOn(event, date) {
+		if (event.all_day || !event.starts_at) return '';
+		if (event.start_day !== iso(date)) return '';
+		return event.starts_at.slice(11, 16);
+	}
+
+	/**
+	 * The calendar's own colour, or nothing.
+	 *
+	 * Checked rather than trusted, even though it comes from Google: this goes into
+	 * an inline `style`, and a value that is not a colour is a value that can close
+	 * the declaration and open another. A hex triple is the whole of what Google
+	 * sends, so anything else is not a colour that failed to render — it is a
+	 * string that has no business being here.
+	 */
+	const HEX = /^#[0-9a-f]{3,8}$/i;
+	const swatch = (colour) => (HEX.test(colour ?? '') ? colour : '');
+
+	/**
+	 * Whether the event links back to Google.
+	 *
+	 * `https:` and nothing else. An href is where a `javascript:` URL becomes a
+	 * click that runs, and the address in this field was written by a service, not
+	 * by the person looking at it.
+	 */
+	const linkOf = (event) => (String(event.url ?? '').startsWith('https://') ? event.url : '');
+
 	const monthName = $derived(
 		cursor.toLocaleDateString(tag(), { month: 'long', year: 'numeric' })
 	);
@@ -232,7 +304,14 @@

 	<div class="grid">
 		{#each grid as date (date.toISOString())}
-			{@const tasks = tasksOn(date)}
+			{@const dayEvents = eventsOn(date)}
+			<!-- Events first, then whatever room is left goes to tasks. An event is
+			     fixed to a time somebody else chose; a task is only dated, and if
+			     something in a full cell has to fall behind "+3 mere", it should be
+			     the one that can be moved. -->
+			{@const tasks = tasksOn(date).slice(0, Math.max(0, chipLimit - dayEvents.length))}
+			{@const hidden =
+				tasksOn(date).length - tasks.length + Math.max(0, dayEvents.length - chipLimit)}
 			<!-- A week has no outside: every day in it is the week you asked for. -->
 			{@const outside = span !== 'week' && date.getMonth() !== cursor.getMonth()}
 			<!-- svelte-ignore a11y_no_static_element_interactions -->
@@ -254,7 +333,36 @@
 				{/if}
 				<span class="number">{date.getDate()}</span>

-				{#each tasks.slice(0, chipLimit) as task (task.id)}
+				{#each dayEvents.slice(0, chipLimit) as event (event.id)}
+					{@const link = linkOf(event)}
+					{@const label = t('cal.eventCannotMove', {
+						name: event.summary,
+						calendar: event.calendar_name || t('cal.title')
+					})}
+					<!-- Not draggable, and it says so twice: the attribute stops the
+					     browser dragging an anchor of its own accord, and the title says
+					     why to anybody who tries. The drop targets would refuse it anyway
+					     — they only accept the task MIME type — but a chip that lifts off
+					     the page and then will not land reads as a bug rather than as a
+					     rule. It is also not a button: there is nothing here to complete,
+					     and a checkbox next to a meeting is an offer verdande cannot keep. -->
+					<svelte:element
+						this={link ? 'a' : 'span'}
+						class="event"
+						class:allday={event.all_day}
+						draggable="false"
+						href={link || undefined}
+						target={link ? '_blank' : undefined}
+						rel={link ? 'noreferrer noopener' : undefined}
+						title={link ? `${label} — ${t('cal.openInGoogle')}` : label}
+						style={swatch(event.colour) ? `--event-colour: ${swatch(event.colour)}` : undefined}
+					>
+						{#if timeOn(event, date)}<span class="at">{timeOn(event, date)}</span>{/if}
+						{event.summary}
+					</svelte:element>
+				{/each}
+
+				{#each tasks as task (task.id)}
 					<!-- Draggable as well as clickable: within a month, moving something
 					     to another day is the whole reason to be looking at a month. The
 					     browser needs a few pixels of movement before it calls a press a
@@ -271,8 +379,8 @@
 					</button>
 				{/each}

-				{#if tasks.length > chipLimit}
-					<span class="more">{t('view.more', { n: tasks.length - chipLimit })}</span>
+				{#if hidden > 0}
+					<span class="more">{t('view.more', { n: hidden })}</span>
 				{/if}
 			</div>
 		{/each}
@@ -451,6 +559,58 @@
 		background: var(--surface);
 	}

+	/* An event reads as a different kind of thing at a glance, before any of the
+	   words are read: a solid bar of colour where a task is a card with a coloured
+	   edge. That is the whole distinction the eye needs — a task is something you
+	   can move and finish, an event is something that is simply happening.
+
+	   The colour is Google's own for that calendar, so two calendars in one grid
+	   are told apart by the colour the person already knows them by. `--line-strong`
+	   is the fallback for a calendar Google gave no colour, which is rare and not
+	   worth a second decision. */
+	.event {
+		--event-colour: var(--line-strong);
+		font-size: var(--text-xs);
+		text-align: left;
+		display: block;
+		padding: 1px var(--s1);
+		border-radius: var(--radius-sm);
+		border-left: 3px solid var(--event-colour);
+		background: var(--surface-sunken);
+		color: var(--ink-muted);
+		text-decoration: none;
+		overflow: hidden;
+		text-overflow: ellipsis;
+		white-space: nowrap;
+		/* A drag that cannot land is worse than one that cannot start. The grab
+		   cursor is the promise; this withholds it. */
+		cursor: default;
+	}
+
+	.event[href] {
+		cursor: pointer;
+	}
+
+	.event:hover {
+		background: var(--surface);
+		color: var(--ink);
+	}
+
+	/* An all-day event has no clock to show, so the colour carries it instead:
+	   filled rather than merely edged, which is what an all-day band looks like in
+	   every calendar anybody has used. */
+	.event.allday {
+		border-left: none;
+		background: color-mix(in oklab, var(--event-colour) 22%, var(--ground));
+		box-shadow: inset 0 0 0 1px color-mix(in oklab, var(--event-colour) 45%, transparent);
+	}
+
+	.at {
+		font-variant-numeric: tabular-nums;
+		color: var(--ink-faint);
+		margin-right: 2px;
+	}
+
 	.more {
 		font-size: var(--text-xs);
 		color: var(--ink-faint);
@@ -482,6 +642,29 @@
 			background: var(--p3);
 		}

+		/* Counted rather than read, like the task chips beside it — a 45px column
+		   fits no title. A bar rather than a dot, so an event is still tellable from
+		   a task at a glance: what the month grid says on a phone is "how much is
+		   on this day, and how much of it is somebody else's". */
+		.event {
+			font-size: 0;
+			padding: 0;
+			height: 4px;
+			border-radius: 1px;
+			border-left: none;
+			box-shadow: none;
+			background: var(--event-colour);
+		}
+
+		.event.allday {
+			background: var(--event-colour);
+			box-shadow: none;
+		}
+
+		.at {
+			display: none;
+		}
+
 		.more {
 			font-size: 10px;
 		}
@@ -536,6 +719,27 @@
 			background: var(--surface-raised);
 		}

+		/* Readable again in the week, for the reason the task chips are: a
+		   full-width row has room for a title, and a week somebody opened on
+		   purpose is one they want to read rather than count. */
+		.calendar.week .event {
+			font-size: var(--text-xs);
+			height: auto;
+			padding: 1px var(--s1);
+			border-radius: var(--radius-sm);
+			border-left: 3px solid var(--event-colour);
+			background: var(--surface-sunken);
+		}
+
+		.calendar.week .event.allday {
+			border-left: none;
+			background: color-mix(in oklab, var(--event-colour) 22%, var(--ground));
+		}
+
+		.calendar.week .at {
+			display: inline;
+		}
+
 		.calendar.week .more {
 			font-size: var(--text-xs);
 		}
@@ -145,7 +145,16 @@
 			// Sidst i rækken, fordi `navOrder` føjer en ukendt nøgle til bagest: står
 			// den et andet sted her, ser en ny konto én rækkefølge og alle
 			// eksisterende en anden.
-			{ key: 'notes', href: '/noter', label: 'notes.title' }
+			{ key: 'notes', href: '/noter', label: 'notes.title' },
+			// Kalenderen bærer et gitter, af samme grund som Noter bærer et ark: den
+			// er ikke endnu et filter over de samme opgaver. Den er de samme opgaver
+			// med noget andet lagt over — Googles begivenheder — og en prik ville
+			// sige, at den hørte til blandt I dag og Kommende.
+			//
+			// Sidst i rækken, fordi `navOrder` føjer en ukendt nøgle til bagest: står
+			// den et andet sted her, ser en ny konto én rækkefølge og alle
+			// eksisterende en anden.
+			{ key: 'calendar', href: '/kalender', label: 'nav.calendar' }
 		].filter(Boolean)
 	);

@@ -488,6 +497,26 @@
 								/>
 								<path d="M9 1.7V5h3.3" fill="none" stroke="currentColor" stroke-width="1.4" />
 							</svg>
+						{:else if item.key === 'calendar'}
+							<svg class="mark" viewBox="0 0 16 16" aria-hidden="true">
+								<rect
+									x="2.2"
+									y="3.2"
+									width="11.6"
+									height="10.6"
+									rx="1.4"
+									fill="none"
+									stroke="currentColor"
+									stroke-width="1.4"
+								/>
+								<path
+									d="M2.2 6.4h11.6M5.6 2.2v2M10.4 2.2v2"
+									fill="none"
+									stroke="currentColor"
+									stroke-width="1.4"
+									stroke-linecap="round"
+								/>
+							</svg>
 						{:else}
 							<span class="dot" class:today={item.key === 'today'} aria-hidden="true"></span>
 						{/if}
@@ -80,6 +80,7 @@ export const da = {
 	'nav.upcoming': 'Kommende',
 	'nav.delegated': 'Venter på andre',
 	'nav.inbox': 'Indbakke',
+	'nav.calendar': 'Kalender',
 	'nav.settings': 'Indstillinger',
 	'nav.signOut': 'Log ud',
 	'nav.main': 'Hovedmenu',
@@ -593,7 +594,7 @@ export const da = {
 		'Klienten er sat i miljøet (VERDANDE_GMAIL_CLIENT_ID), så den kan ikke ændres her. Det er med vilje: en værdi i runens manifest er en beslutning, der bliver anvendt igen ved hver genstart, og en formular, der kunne overskrive den, ville gøre manifestet til en løgn.',
 	'int.oauthClient': 'OAuth-klient hos Google',
 	'int.registerHint':
-		'Registrér en klient i Google Cloud Console → APIs & Services → Credentials → OAuth client ID → Web application, slå Gmail API til, og indsæt de to værdier her. Din egen konto skal stå som testbruger, så længe appen ikke er verificeret hos Google.',
+		'Registrér en klient i Google Cloud Console → APIs & Services → Credentials → OAuth client ID → Web application, og indsæt de to værdier her. Den samme klient bruges til både Gmail og Google Kalender: slå det API til, du skal bruge, og tilføj begge redirect-URI\'er — den nedenfor og kalenderens, som står i panelet Google Kalender. Din egen konto skal stå som testbruger, så længe appen ikke er verificeret hos Google.',
 	'int.redirectURI': 'Godkendt redirect-URI',
 	'int.clientID': 'Klient-id',
 	'int.clientSecret': 'Klienthemmelighed',
@@ -633,6 +634,32 @@ export const da = {
 	'int.server': 'Server',
 	'int.caldavAuth':
 		'Brugernavn er din e-mail. Adgangskoden er en API-token — ikke din rigtige adgangskode.',
+	'int.calendar': 'Google Kalender',
+	'int.calendarHint':
+		'Læses, aldrig skrives. Begivenhederne vises i Kalender ved siden af dine egne opgaver med forfaldsdato — de kan ikke flyttes eller lukkes herfra, for de hører til i Google.',
+	'int.connectCalendar': 'Forbind Google Kalender',
+	'int.calendarConnectedAs': 'Forbundet som',
+	'int.calendarSameClient':
+		'Bruger den samme OAuth-klient som Gmail ovenfor. Google Calendar API skal være slået til, og denne adresse skal stå som godkendt redirect-URI.',
+	'int.whichCalendars': 'Hvilke kalendere vises',
+	'int.noCalendars': 'Kontoen har ingen kalendere at vise.',
+	'int.calendarLastSync': 'Sidst hentet {when}.',
+	'int.calendarNeverSynced': 'Ikke hentet endnu.',
+	'int.calendarFetchedOne': '{n} begivenhed hentet.',
+	'int.calendarFetchedMany': '{n} begivenheder hentet.',
+	'int.calendarNothingNew': 'Ingen begivenheder i vinduet.',
+	'int.calendarConnected': 'Google Kalender er forbundet.',
+	'int.calendarState':
+		'Svaret fra Google passede ikke til det forsøg, der blev startet her. Prøv igen.',
+	'int.calendarExpired': 'Forsøget udløb undervejs. Prøv igen.',
+	'int.calendarInvalid': 'Svaret fra Google kunne ikke læses. Prøv igen.',
+	'int.calendarFailed': 'Google afviste ombytningen af koden.',
+	'int.calendarNoRefresh':
+		'Google sendte ingen refresh-token. Fjern verdande under din Google-konto og forbind igen.',
+	'int.calendarDenied': 'Adgangen blev afvist hos Google.',
+	'int.calendarOrgInternal':
+		'Google-appen er registreret som Internal og tager kun imod konti i organisationen. En privat konto kan ikke godkende den, uanset hvad der står på skærmen.',
+	'int.calendarOther': 'Google svarede: {what}',
 	'int.gmailFetchedOne': '{n} opgave hentet.',
 	'int.gmailFetchedMany': '{n} opgaver hentet.',
 	'int.gmailNothingNew': 'Ingen nye beskeder.',
@@ -647,6 +674,18 @@ export const da = {
 	'int.gmailDenied': 'Adgangen blev afvist hos Google.',
 	'int.gmailOther': 'Gmail svarede: {what}',

+	// --- kalenderen, med Googles begivenheder lagt over ---------------------------------
+	'cal.title': 'Kalender',
+	'cal.notConnected':
+		'Ingen kalender er forbundet endnu. Det gøres under Indstillinger → Integrationer.',
+	'cal.settings': 'Indstillinger',
+	'cal.noneChosen': 'Ingen af kontoens kalendere er valgt endnu.',
+	'cal.allDay': 'Hele dagen',
+	'cal.openInGoogle': 'Åbn i Google Kalender',
+	'cal.beyondWindow':
+		'Begivenheder gemmes fra {from} til {to}. Uden for det viser gitteret kun dine egne opgaver.',
+	'cal.eventCannotMove': '{name} — en begivenhed i {calendar}. Den kan ikke flyttes herfra.',
+
 	// --- a project ----------------------------------------------------------------------
 	'project.name': 'Projektets navn',
 	'project.clickToRename': 'Klik for at omdøbe',
@@ -789,6 +828,10 @@ export const da = {
 		'Denne instans kan ikke genstarte sig selv: {missing} er ikke sat. En container kan ikke udskifte sit eget image — panelet gør arbejdet, og det her er kun måden at bede om det.',

 	'error.gmailSaid': 'Gmail svarede: {what}',
+	'error.calendarRefused': 'Google afviste kaldet. Prøv at forbinde kalenderen igen.',
+	'error.calendarSaid': 'Google svarede: {what}',
+	'int.disconnectCalendarQuestion':
+		'Afbryd forbindelsen til Google Kalender? Tokens bliver glemt, og den hentede kopi af begivenhederne bliver slettet. Dine egne opgaver rører den ikke.',

 	'error.mailboxRefused': 'Postkassen kunne ikke læses.',
 	'error.mailboxSaid': 'Postkassen svarede: {what}',
@@ -76,6 +76,7 @@ export const en = {
 	'nav.upcoming': 'Upcoming',
 	'nav.delegated': 'Waiting on others',
 	'nav.inbox': 'Inbox',
+	'nav.calendar': 'Calendar',
 	'nav.settings': 'Settings',
 	'nav.signOut': 'Sign out',
 	'nav.main': 'Main menu',
@@ -589,7 +590,7 @@ export const en = {
 		'The client is set in the environment (VERDANDE_GMAIL_CLIENT_ID), so it cannot be changed here. That is deliberate: a value in the Rune’s manifest is a decision reapplied on every restart, and a form that could overwrite it would make the manifest a lie.',
 	'int.oauthClient': 'OAuth client at Google',
 	'int.registerHint':
-		'Register a client in Google Cloud Console → APIs & Services → Credentials → OAuth client ID → Web application, enable the Gmail API, and paste the two values here. Your own account has to be listed as a test user for as long as the app is unverified with Google.',
+		'Register a client in Google Cloud Console → APIs & Services → Credentials → OAuth client ID → Web application and paste the two values here. The same client serves both Gmail and Google Calendar: enable whichever API you need, and add both redirect URIs — the one below and the calendar\'s, which is shown in the Google Calendar panel. Your own account has to be listed as a test user for as long as the app is unverified with Google.',
 	'int.redirectURI': 'Authorised redirect URI',
 	'int.clientID': 'Client ID',
 	'int.clientSecret': 'Client secret',
@@ -629,6 +630,31 @@ export const en = {
 	'int.server': 'Server',
 	'int.caldavAuth':
 		'The username is your email. The password is an API token — not your real password.',
+	'int.calendar': 'Google Calendar',
+	'int.calendarHint':
+		'Read, never written. The events appear in Calendar beside your own tasks with due dates — they cannot be moved or completed from here, because they belong to Google.',
+	'int.connectCalendar': 'Connect Google Calendar',
+	'int.calendarConnectedAs': 'Connected as',
+	'int.calendarSameClient':
+		'Uses the same OAuth client as Gmail above. The Google Calendar API has to be enabled, and this address has to be listed as an authorised redirect URI.',
+	'int.whichCalendars': 'Which calendars are shown',
+	'int.noCalendars': 'The account has no calendars to show.',
+	'int.calendarLastSync': 'Last fetched {when}.',
+	'int.calendarNeverSynced': 'Not fetched yet.',
+	'int.calendarFetchedOne': '{n} event fetched.',
+	'int.calendarFetchedMany': '{n} events fetched.',
+	'int.calendarNothingNew': 'No events in the window.',
+	'int.calendarConnected': 'Google Calendar is connected.',
+	'int.calendarState': 'Google’s reply did not match the attempt that started here. Try again.',
+	'int.calendarExpired': 'The attempt expired on the way. Try again.',
+	'int.calendarInvalid': 'Google’s reply could not be read. Try again.',
+	'int.calendarFailed': 'Google refused to exchange the code.',
+	'int.calendarNoRefresh':
+		'Google sent no refresh token. Remove verdande from your Google account and connect again.',
+	'int.calendarDenied': 'Access was refused at Google.',
+	'int.calendarOrgInternal':
+		'The Google app is registered as Internal and only accepts accounts inside the organisation. A private account cannot consent to it, whatever the screen says.',
+	'int.calendarOther': 'Google replied: {what}',
 	'int.gmailFetchedOne': '{n} task fetched.',
 	'int.gmailFetchedMany': '{n} tasks fetched.',
 	'int.gmailNothingNew': 'No new messages.',
@@ -642,6 +668,17 @@ export const en = {
 	'int.gmailDenied': 'Access was refused at Google.',
 	'int.gmailOther': 'Gmail replied: {what}',

+	// --- the calendar, with Google’s events laid over ------------------------------------
+	'cal.title': 'Calendar',
+	'cal.notConnected': 'No calendar is connected yet. That is done under Settings → Integrations.',
+	'cal.settings': 'Settings',
+	'cal.noneChosen': 'None of the account’s calendars are chosen yet.',
+	'cal.allDay': 'All day',
+	'cal.openInGoogle': 'Open in Google Calendar',
+	'cal.beyondWindow':
+		'Events are kept from {from} to {to}. Outside that the grid shows only your own tasks.',
+	'cal.eventCannotMove': '{name} — an event in {calendar}. It cannot be moved from here.',
+
 	// --- a project ----------------------------------------------------------------------
 	'project.name': 'The project’s name',
 	'project.clickToRename': 'Click to rename',
@@ -784,6 +821,10 @@ export const en = {
 		'This instance cannot restart itself: {missing} are not set. A container cannot replace its own image — the panel does the work, and this is only the way to ask.',

 	'error.gmailSaid': 'Gmail said: {what}',
+	'error.calendarRefused': 'Google refused the call. Try connecting the calendar again.',
+	'error.calendarSaid': 'Google replied: {what}',
+	'int.disconnectCalendarQuestion':
+		'Disconnect Google Calendar? The tokens are forgotten and the fetched copy of the events is deleted. Your own tasks are untouched.',

 	'error.mailboxRefused': 'The mailbox could not be read.',
 	'error.mailboxSaid': 'The mailbox answered: {what}',
@@ -835,6 +835,43 @@ function read() {

 export const upcomingView = new UpcomingView();

+/**
+ * Month or week on Kalender.
+ *
+ * Its own key rather than Kommende's, even though the two switchers look alike.
+ * They are not the same choice: Kommende opens on a list of the next seven days
+ * and offers a grid, and Kalender is the grid — sharing the value would mean
+ * choosing a week on one and finding the other had changed, and one of them would
+ * have to answer for the `list` mode the other does not have.
+ *
+ * In localStorage rather than on the account, and for the same reason as the
+ * sidebar's width: a grid of seven columns needs room, and the answer on a phone
+ * is not the answer on a wide monitor.
+ */
+const CALENDAR_MODES = ['week', 'month'];
+
+class CalendarViewMode {
+	mode = $state(readCalendarMode());
+
+	set(next) {
+		if (!CALENDAR_MODES.includes(next)) return;
+		this.mode = next;
+		try {
+			localStorage.setItem('verdande:calendar', next);
+		} catch {
+			// Private browsing; the choice simply will not persist.
+		}
+	}
+}
+
+function readCalendarMode() {
+	if (typeof localStorage === 'undefined') return 'month';
+	const stored = localStorage.getItem('verdande:calendar');
+	return CALENDAR_MODES.includes(stored) ? stored : 'month';
+}
+
+export const calendarView = new CalendarViewMode();
+
 /**
 * Whether the lists show what has already been finished.
 *
@@ -1,9 +1,9 @@
 <script>
-	/** Gmail, the calendar feed, and the mail-to-task address. */
+	/** Gmail, Google Calendar, the calendar feed, and the mail-to-task address. */
 	import { api, humanMessage } from '$lib/api.js';
 	import { app } from '$lib/stores.svelte.js';
 	import { page } from '$app/stores';
-	import { t, plural } from '$lib/i18n.svelte.js';
+	import { t, plural, tag } from '$lib/i18n.svelte.js';

 	// --- Gmail ------------------------------------------------------------------

@@ -136,6 +136,120 @@
 		}
 	}

+	// --- Google Calendar -----------------------------------------------------------
+
+	// Its own panel rather than a second mode inside the Gmail one. They sign in
+	// through the same registration and are otherwise nothing alike: one turns mail
+	// into work you own, the other shows a copy of somebody else's calendar and
+	// never writes to it.
+	let calendar = $state(null);
+	let savingCalendars = $state(false);
+	let calendarsSaved = $state(false);
+	let syncingCalendar = $state(false);
+	/** The ids ticked in the form, which is not what is stored until Save. */
+	let shownCalendars = $state([]);
+
+	const CALENDAR_CALLBACK = {
+		connected: { tone: 'ok', text: t('int.calendarConnected') },
+		state: { tone: 'bad', text: t('int.calendarState') },
+		expired: { tone: 'bad', text: t('int.calendarExpired') },
+		invalid: { tone: 'bad', text: t('int.calendarInvalid') },
+		failed: { tone: 'bad', text: t('int.calendarFailed') },
+		norefresh: { tone: 'bad', text: t('int.calendarNoRefresh') },
+		access_denied: { tone: 'bad', text: t('int.calendarDenied') },
+		// The one worth naming. An OAuth app registered as Internal accepts only
+		// accounts inside the organisation, and Google's own screen does not say
+		// that in words anybody could act on.
+		org_internal: { tone: 'bad', text: t('int.calendarOrgInternal') }
+	};
+
+	let calendarCallback = $derived.by(() => {
+		const value = $page.url.searchParams.get('calendar');
+		if (!value) return null;
+		return CALENDAR_CALLBACK[value] ?? { tone: 'bad', text: t('int.calendarOther', { what: value }) };
+	});
+
+	$effect(() => {
+		loadCalendar();
+	});
+
+	async function loadCalendar() {
+		try {
+			calendar = await api.getCalendar();
+			shownCalendars = calendar.calendars.filter((c) => c.shown).map((c) => c.id);
+		} catch (e) {
+			app.toast(humanMessage(e));
+		}
+	}
+
+	async function connectCalendar() {
+		try {
+			const { url } = await api.authorizeCalendar();
+			location.href = url;
+		} catch (e) {
+			app.toast(humanMessage(e));
+		}
+	}
+
+	async function saveCalendars(event) {
+		event.preventDefault();
+		savingCalendars = true;
+		calendarsSaved = false;
+		try {
+			await api.setCalendars(shownCalendars);
+			calendarsSaved = true;
+			// And fetch, without being asked again.
+			//
+			// Ticking a calendar is somebody saying "show me this one". Saving the
+			// choice and leaving the grid empty until the sweep comes round a quarter
+			// of an hour later is a calendar that says a fortnight is clear — and the
+			// person is on this page, watching, with the button under their hand.
+			// Also what refreshes the panel: syncCalendarNow reloads it when it is done.
+			if (shownCalendars.length) {
+				await syncCalendarNow();
+			} else {
+				await loadCalendar();
+			}
+		} catch (e) {
+			app.toast(humanMessage(e));
+		} finally {
+			savingCalendars = false;
+		}
+	}
+
+	async function syncCalendarNow() {
+		syncingCalendar = true;
+		try {
+			const result = await api.syncCalendar();
+			app.toast(
+				result?.events
+					? plural(result.events, 'int.calendarFetchedOne', 'int.calendarFetchedMany')
+					: t('int.calendarNothingNew')
+			);
+			await loadCalendar();
+		} catch (e) {
+			app.toast(humanMessage(e));
+		} finally {
+			syncingCalendar = false;
+		}
+	}
+
+	async function disconnectCalendar() {
+		if (!confirm(t('int.disconnectCalendarQuestion'))) return;
+		try {
+			await api.disconnectCalendar();
+			await loadCalendar();
+		} catch (e) {
+			app.toast(humanMessage(e));
+		}
+	}
+
+	function toggleCalendar(id) {
+		shownCalendars = shownCalendars.includes(id)
+			? shownCalendars.filter((c) => c !== id)
+			: [...shownCalendars, id];
+	}
+
 	// --- calendar feed -------------------------------------------------------------

 	let feedURL = $state('');
@@ -355,6 +469,87 @@
 	{/if}
 </section>

+<section class="panel">
+	<header>
+		<h2>{t('int.calendar')}</h2>
+		<p class="hint">{t('int.calendarHint')}</p>
+	</header>
+
+	{#if calendarCallback}
+		<p class="callback" data-tone={calendarCallback.tone}>{calendarCallback.text}</p>
+	{/if}
+
+	{#if calendar === null}
+		<p class="empty">…</p>
+	{:else if !calendar.connected}
+		<div class="row">
+			<button class="primary" onclick={connectCalendar} disabled={!calendar.has_client}>
+				{t('int.connectCalendar')}
+			</button>
+		</div>
+
+		<!-- The registration is the Gmail panel's — one client, two features — so
+		     this only spells out the second redirect URI, which has to be added to
+		     it. It is the single most likely thing to be wrong, and the error Google
+		     gives for it names neither value. -->
+		{#if app.user?.is_admin}
+			<div class="field">
+				<label for="calendar-redirect">{t('int.redirectURI')}</label>
+				<input id="calendar-redirect" class="mono" readonly value={calendar.redirect_uri} />
+				<p class="hint">{t('int.calendarSameClient')}</p>
+			</div>
+		{:else if !calendar.has_client}
+			<p class="hint">{t('int.noClient')}</p>
+		{/if}
+	{:else}
+		<p class="hint">
+			{t('int.calendarConnectedAs')}
+			<strong>{calendar.account || t('int.unknownAccount')}</strong>.
+		</p>
+
+		<form onsubmit={saveCalendars}>
+			{#if calendar.calendars.length}
+				<fieldset>
+					<legend>{t('int.whichCalendars')}</legend>
+					{#each calendar.calendars as c (c.id)}
+						<label class="pick">
+							<input
+								type="checkbox"
+								checked={shownCalendars.includes(c.id)}
+								onchange={() => toggleCalendar(c.id)}
+							/>
+							<!-- Google's own colour for the calendar, which is what the grid
+							     draws its events in. Told apart by the colour the person
+							     already knows it by, not by one of verdande's ten names. -->
+							<span class="swatch" style:background={c.colour || 'var(--line-strong)'}></span>
+							{c.name}
+						</label>
+					{/each}
+				</fieldset>
+			{:else}
+				<p class="hint">{t('int.noCalendars')}</p>
+			{/if}
+
+			<p class="hint">
+				{calendar.last_sync_at
+					? t('int.calendarLastSync', {
+							when: new Date(calendar.last_sync_at).toLocaleString(tag())
+						})
+					: t('int.calendarNeverSynced')}
+			</p>
+
+			<div class="row">
+				<button class="primary" type="submit" disabled={savingCalendars}>{t('int.save')}</button>
+				{#if calendarsSaved}<span class="saved">{t('int.saved')}</span>{/if}
+				<button class="secondary" onclick={syncCalendarNow} disabled={syncingCalendar}>
+					{syncingCalendar ? t('int.fetching') : t('int.fetchNow')}
+				</button>
+				<button class="danger" onclick={disconnectCalendar}>{t('int.disconnect')}</button>
+			</div>
+		</form>
+	{/if}
+</section>
+
 <section class="panel">
 	<header>
 		<h2>{t('int.feed')}</h2>
@@ -529,6 +724,38 @@
 		border-color: var(--danger);
 	}

+	fieldset {
+		border: 1px solid var(--line);
+		border-radius: var(--radius);
+		padding: var(--s3);
+		display: flex;
+		flex-direction: column;
+		gap: var(--s2);
+	}
+
+	legend {
+		font-size: var(--text-sm);
+		color: var(--ink-muted);
+		padding: 0 var(--s1);
+	}
+
+	.pick {
+		display: flex;
+		align-items: center;
+		gap: var(--s2);
+		font-size: var(--text-sm);
+	}
+
+	/* A solid mark beside a label that carries the meaning, so it only has to be
+	   tellable from its neighbours and visible on both near-black and white — the
+	   same job the project colours' dots do. */
+	.swatch {
+		width: 10px;
+		height: 10px;
+		border-radius: var(--radius-full);
+		flex: none;
+	}
+
 	a {
 		color: var(--accent);
 	}
@@ -0,0 +1,195 @@
+<script>
+	/**
+	 * Kalender: Google's events and verdande's own dated tasks in one grid.
+	 *
+	 * The same component Kommende uses, given a second list to draw. Not a second
+	 * grid, and the reason is the part that is easy to get subtly wrong: a drop
+	 * target has to decide from `dataTransfer.types` alone whether it accepts a
+	 * drag, and a second copy of that is a second place for it to be almost right.
+	 * A task dragged here reschedules exactly as it does everywhere else, because
+	 * it is the same code doing it.
+	 *
+	 * A month and a week, and no list. The list is Kommende's answer — seven days
+	 * of work, in order — and this view is the other question: what does the day
+	 * already have in it.
+	 */
+	import { api, humanMessage } from '$lib/api.js';
+	import { app, calendarView } from '$lib/stores.svelte.js';
+	import CalendarView from '$lib/components/CalendarView.svelte';
+	import { t } from '$lib/i18n.svelte.js';
+
+	let events = $state([]);
+	/** Null until the first answer, so nothing flashes before it is known. */
+	let window_ = $state(null);
+	let connected = $state(null);
+	/** Whether any calendar in the connected account is ticked. */
+	let anyShown = $state(false);
+	/** The dates the grid is showing, so the notice below can compare against them. */
+	let showing = $state(null);
+
+	$effect(() => {
+		api
+			.getCalendar()
+			.then((status) => {
+				connected = status.connected;
+				anyShown = (status.calendars ?? []).some((c) => c.shown);
+			})
+			.catch(() => {
+				// A calendar that could not be asked about is not a reason to withhold
+				// the grid: the tasks in it are verdande's own and do not depend on
+				// Google being reachable.
+				connected = false;
+			});
+	});
+
+	/**
+	 * Loads the dates a grid is showing, whichever grid it is.
+	 *
+	 * Both halves at once, because they answer the same question about the same
+	 * cells. The limit on the tasks is raised well above the default for the reason
+	 * Kommende raises it: a busy month across every project is more than two hundred
+	 * rows, and a silently truncated grid is a calendar that quietly lies about a
+	 * day being clear.
+	 */
+	function loadRange({ from, to }) {
+		showing = { from, to };
+		app.loadTasks({ due_from: from, due_before: to, limit: 500 });
+		api
+			.calendarEvents(from, to)
+			.then((data) => {
+				events = data.events;
+				window_ = { from: data.from, to: data.to };
+			})
+			.catch((e) => {
+				// The grid still draws, with the tasks in it. Saying so once beats a
+				// view that renders half of itself and explains nothing.
+				events = [];
+				app.toast(humanMessage(e));
+			});
+	}
+
+	// Whether the grid has been paged past the window verdande keeps a copy of.
+	//
+	// Said out loud rather than left as an empty month. A calendar showing no events
+	// looks exactly like a calendar with no events in it, and the difference between
+	// "nothing is booked" and "I have not looked that far" is the whole reason
+	// somebody opened this.
+	let beyond = $derived(
+		connected &&
+			window_ &&
+			showing &&
+			(showing.from < window_.from || showing.to > window_.to)
+	);
+</script>
+
+<div class="view">
+	<header>
+		<h1>{t('cal.title')}</h1>
+		<div class="views" role="group" aria-label={t('view.mode')}>
+			{#each [['week', t('view.week')], ['month', t('view.month')]] as [value, label]}
+				<button
+					class:active={calendarView.mode === value}
+					onclick={() => calendarView.set(value)}
+					aria-pressed={calendarView.mode === value}>{label}</button
+				>
+			{/each}
+		</div>
+	</header>
+
+	{#if connected === false}
+		<!-- Shown once, and quietly. The grid underneath is already useful without a
+		     Google account in it — it is verdande's own calendar, which is what this
+		     view was before anything was laid over it. -->
+		<p class="hint">
+			{t('cal.notConnected')}
+			<a href="/indstillinger/integrationer">{t('cal.settings')}</a>
+		</p>
+	{/if}
+
+	<!-- Connected, and nothing ticked. Worth its own sentence rather than an empty
+	     grid: "no calendar is chosen" and "nothing is booked" look identical, and
+	     only one of them is something to do about. -->
+	{#if connected && !anyShown}
+		<p class="hint">
+			{t('cal.noneChosen')}
+			<a href="/indstillinger/integrationer">{t('cal.settings')}</a>
+		</p>
+	{/if}
+
+	{#if beyond}
+		<p class="hint">{t('cal.beyondWindow', { from: window_.from, to: window_.to })}</p>
+	{/if}
+
+	{#if calendarView.mode === 'week'}
+		<CalendarView span="week" {events} onrange={loadRange} />
+	{:else}
+		<CalendarView {events} onrange={loadRange} />
+	{/if}
+</div>
+
+<style>
+	/* A month grid needs the width a reading column deliberately withholds — the
+	   same allowance Kommende and the project page make for theirs. */
+	.view {
+		max-width: 1400px;
+		margin: 0 auto;
+		padding: var(--s6) var(--s4) var(--s8);
+	}
+
+	/* Wraps, for the same reason the project header does: a title and a switcher
+	   are more than a phone's width, and the switcher belongs underneath rather
+	   than squeezing the heading. */
+	header {
+		display: flex;
+		align-items: center;
+		gap: var(--s3);
+		flex-wrap: wrap;
+		margin-bottom: var(--s5);
+	}
+
+	h1 {
+		font-size: var(--text-2xl);
+		flex: 1 1 8ch;
+		min-width: 8ch;
+	}
+
+	.views {
+		display: flex;
+		gap: 1px;
+		flex: none;
+		background: var(--line);
+		border: 1px solid var(--line);
+		border-radius: var(--radius);
+		overflow: hidden;
+	}
+
+	.views button {
+		padding: var(--s1) var(--s3);
+		font-size: var(--text-sm);
+		background: var(--ground);
+		color: var(--ink-muted);
+		transition:
+			background var(--fast) var(--ease),
+			color var(--fast) var(--ease);
+	}
+
+	.views button:hover {
+		color: var(--ink);
+	}
+
+	.views button.active {
+		background: var(--surface-raised);
+		color: var(--ink);
+		font-weight: 500;
+	}
+
+	.hint {
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Author	SHA1	Message	Date
Kristian WindandClaude Opus 5	bdde9cc6a5	merge: Google Kalender som menupunkt, med Verdandes egen kalender lagt over Release / Build and publish image (push) Failing after 9m58s Details Læs bredt, skriv snævert — decision 5 i planen, og kun den første halvdel: kalenderen læses, og der skrives ingenting tilbage. OAuth-blokeringen er reel og blev ikke gået udenom. En klient registreret som Internal tager kun konti i sit eget workspace — også til kalendere, ikke kun Gmail. Andreas' private konto bliver afvist med `org_internal`, og det er klienten, der virker efter hensigten, ikke en fejl. Fladen siger det nu med ord, man kan handle på, frem for at vise Googles egen skærm, der ikke gør. Vejen udenom, som ikke er bygget: kalenderens egen hemmelige ICS-adresse. Ingen OAuth, virker for enhver konto, og `internal/ics` findes allerede. Det er det næste stykke, og det eneste, der låser den private konto op. `internal/google` er flyttet ud af `internal/gmail`, fordi de to er det samme flow, der er uenige om én streng. Egen callback-adresse frem for at dele Gmails: én callback, der finder ud af hvilken token-butik den skal skrive i, går galt ved at overskrive en Gmail-forbindelse, der virkede. Egne tabeller frem for `mailboxes`. `trigger_kind`, `seen` og `last_uid` svarer alle på "hvad gør en besked til en opgave", og ingenting her bliver til en opgave; én konto har mange kalendere, og `mailboxes` har ikke plads til en en-til-mange. Afgørende i praksis: `mailboxes.kind` har en CHECK, og SQLite kan ikke ændre en — en tredje værdi koster den tabelombygning, som migration 0021 skulle igennem. Begivenheder erstattes pr. kalender pr. vindue frem for at flettes med et sync-token: et vindue, der slettes og skrives forfra, kan ikke komme ud af trit, og et sync-token er endnu en ting, der skal være rigtig for altid, for at gitteret ikke stille viser noget forkert. `CalendarView` er udvidet, ikke kopieret. En begivenhed er et fyldt bånd, hvor en opgave er et kort med en farvet kant, så de to læses forskelligt før et ord er læst — og den kan ikke trækkes og er aldrig en knap: der er ikke noget at gøre færdigt ved en andens møde. To værn på det, der kommer fra Google: farven skal matche et hex-mønster, før den må stå i en style, og linket bliver kun til et href, hvis det begynder med https. Konflikten i jobs.go var to nye jobs skrevet på samme linje. Begge skal med. Co-Authored-By: Claude Opus 5 <[email protected]>	2026-08-20 07:39:12 +02:00
Kristian Wind	dcd66b415e	docs(web): registreringsteksten fortæller nu, at klienten dækker begge dele Hjælpeteksten sagde "slå Gmail API til", og det er kun det halve nu. Den samme klient bærer både Gmail og Google Kalender og skal have begge redirect-URI'er — og kalenderpanelet siger, hvor dets egen kommer fra, så ingen leder efter et felt til en klienthemmelighed, der allerede står ovenfor.	2026-08-20 07:33:24 +02:00
Kristian Wind	a5f2f769c4	fix(web): begivenhederne i en celle sorteres, hvor de tegnes Serveren sorterer allerede, men en celle, der viser 14:00 over 09:15, ligner ikke en liste i forkert rækkefølge — den ligner et forkert klokkeslæt på chippen, og det er langt værre at skulle udelukke. Heldags først: en heldags begivenhed er et bånd hen over dagen, ikke noget der sker på et punkt i den.	2026-08-20 07:30:55 +02:00
Kristian Wind	031bb18067	fix(calendar): en tom kalender skal sige hvorfor, ikke bare være tom At vælge en kalender er nogen, der siger "vis mig den her". At gemme valget og lade gitteret stå tomt, til fejeren kommer forbi et kvarter senere, er en kalender, der påstår, at fjorten dage er fri — og personen står på siden med knappen under hånden. Gemningen henter nu selv. Og er der forbundet en konto uden at der er valgt nogen kalendere, siger visningen dét. "Der er ikke valgt en kalender" og "der er ikke booket noget" ser ens ud, og kun den ene er noget at gøre noget ved.	2026-08-20 07:27:42 +02:00
Kristian Wind	1b1e57df29	docs: kalenderen den anden vej, og én registrering til begge Google-ting `caldav.md` beskrev to måder at sende opgaver ud. Den tredje er den modsatte retning og hører til samme sted, fordi det er dér, man ville lede. `configuration.md` hed "Gmail" og handler nu om Google: samme klient, to redirect-URI'er, to API'er, to scopes. Bemærkningen om en Internal-app står begge steder, fordi den gælder begge veje — og for én privat konto er kalenderens egen hemmelige ICS-adresse den kortere vej. Intet i verdande abonnerer på sådan en endnu.	2026-08-20 07:24:01 +02:00
Kristian Wind	c3f2181efe	feat(web): Kalender som menupunkt, med Googles begivenheder lagt over egne opgaver Samme gitter som Kommende, givet en liste mere at tegne. Ikke et gitter nummer to, og grunden er den del, der er nem at få næsten rigtig: et mål skal afgøre ud fra `dataTransfer.types` alene, om det tager imod, og to kopier af det er to steder at være næsten rigtig. En opgave trukket her flyttes præcis som alle andre steder, fordi det er den samme kode, der gør det. En begivenhed er ikke en opgave, og cellen siger det før et eneste ord er læst: en flade af farve, hvor en opgave er et kort med en farvet kant. Den kan ikke trækkes — forbindelsen er læsende, og en chip, der letter fra siden og så ikke vil lande, læses som en fejl frem for som en regel — og den er ikke en knap, for der er ikke noget at lukke ved en andens møde. Farven er Googles egen for den kalender, så to kalendere i ét gitter kendes fra hinanden på den farve, personen allerede kender dem på. Farven tjekkes frem for at blive troet: den ender i en inline `style`, og en værdi, der ikke er en farve, kan lukke erklæringen og åbne en anden. Linket tegnes kun, hvis det begynder med `https://` — et href er dér, hvor en `javascript:`-adresse bliver til et klik, der kører. Prøven bruger uge-visningen med vilje: en månedscelle skæres af ved tre chips, og resten af suiten lægger opgaver på andre dage. Datoen læses ud af siden, ikke ud af testprocessen, som de øvrige har lært at gøre.	2026-08-20 07:22:25 +02:00
Kristian Wind	987d4edfce	feat(calendar): en læst Google-kalender, med sit eget endpoint og sin egen sweep Samme registrering som Gmail, et andet scope og en anden redirect-URI. Google udsteder en refresh-token pr. godkendelse og holder op til hundrede i live pr. konto, hver med sine egne scopes — så en forbundet kalender rører ikke en Gmail, der virker, og at afbryde den ene tager ikke den anden med. Callbacken har sin egen sti. Én callback, der ud fra gemt tilstand afgjorde, hvilket af de to flows der kom tilbage, ville lægge valget af hvilket token-lager der skrives bag et opslag — og går det galt, går det galt ved at overskrive en virkende Gmail-forbindelse med kalender-tokens. Begivenhederne caches i et vindue på 90 dage tilbage og et år frem. Et månedsgitter bladrer, og et kald til Google pr. piletast er en kalender, der er langsommere end den kalender, den viser. Vinduet har en kant, og endpointet siger hvor den er: et tomt svar uden forklaring er en kalender, der lydløst påstår, at en dag er fri.	2026-08-20 07:01:14 +02:00
Kristian Wind	7828c1e6ed	feat(gcal): Google Calendar kan læses, og kalenderen får sine egne tabeller Klienten henter kalenderlisten og begivenhederne i et vindue, og laver Googles to former om til den ene, et gitter kan spørge om: dage i begge ender, begge med. Googles heldags-slutdato er eksklusiv, og et møde, der slutter ved midnat, slutter aftenen før — begge dele rettes ét sted frem for hos hver læser. Egne tabeller frem for `mailboxes`. De to ligner hinanden på afstand og er uenige om hver eneste kolonne bagefter: `trigger_kind`, `seen`, `last_uid` og `project_id` svarer alle på "hvad laver en besked om til en opgave", og intet her bliver til en opgave. Én konto rummer desuden mange kalendere, og en en-til-mange er der ikke plads til. Det afgørende er mindre og mere praktisk: `mailboxes.kind` har en CHECK, og SQLite kan ikke ændre en CHECK — en tredje værdi koster en tabelombygning med fremmednøgler slået fra. Derfor er der ingen CHECK på `provider` her: CalDAV skal koste en række, ikke en ombygning.	2026-08-20 06:50:57 +02:00
Kristian Wind	a46d9158e1	refactor(google): OAuth-flowet flytter ud af gmail, så to ting kan dele det Gmail og Google Calendar logger ind gennem den samme registrering med den samme PKCE og den samme fornyelse. Det eneste, der adskiller dem, er ét ord: scopet. En kopi mere ville være et sted mere, hvor `access_type=offline` kan blive glemt — og det er dén fejl, der får en forbindelse til at dø lydløst en time efter, den blev lavet. internal/gmail beholder sit API og sit scope; navnene på flowet er aliaser, så hverken kaldere eller prøver ændrer sig. Prøverne for PKCE, AuthURL og Configured flytter med koden.	2026-08-20 06:46:10 +02:00