diff --git a/README.md b/README.md
index 94e04f3..8474841 100644
--- a/README.md
+++ b/README.md
@@ -302,6 +302,8 @@ the agenda kept up so `:repeat` acts on the card, `H` / `L` send it to
 the list left / right on its board, and `T` writes today's entry. The bar shows `late` and `today` counts
 whenever either is above zero, and the agenda opens by itself once a day when
 something is late or due, so nothing has to be remembered to be looked at.
+The day is the one in `WORKSPACE_TIMEZONE`, as for the mails, so a browser on a
+trip groups the cards the same way.
 Below the cards it lists what the diary holds from this day in earlier years;
 `j` walks on into them and `Enter` opens one. A 29 February is remembered on
 the 28th in the years that have none.
@@ -846,7 +848,7 @@ sealed or not.
 | `DELETE` | `/api/trash/{id}` | delete one thing in the trash for good |
 | `POST` | `/api/trash/{id}/restore` | back where it was deleted from, or to its space when that folder is gone |
 | `GET` | `/api/spaces/{id}/board` | the lists and cards of one space |
-| `GET` | `/api/agenda` | open cards due within a week or in hand, on every board, whether the diary has today, and its entries `on_this_day` in earlier years |
+| `GET` | `/api/agenda` | open cards due within a week or in hand, on every board, whether the diary has today, its entries `on_this_day` in earlier years, and `today` in `WORKSPACE_TIMEZONE`, with its bounds |
 | `GET` | `/api/diary/days?month=2026-10` | the diary's entries in a month, each with its local `day` |
 | `GET` | `/api/diary/around/{id}` | the entries before and after a diary entry, by date |
 | `GET` | `/api/nodes/{id}/templates` | the templates of the space the node is in |
diff --git a/docs/wiki/API.md b/docs/wiki/API.md
index 8aef60d..b1baa07 100644
--- a/docs/wiki/API.md
+++ b/docs/wiki/API.md
@@ -20,7 +20,7 @@ sealed or not.
 | `DELETE` | `/api/trash/{id}` | delete one thing in the trash for good |
 | `POST` | `/api/trash/{id}/restore` | back where it was deleted from, or to its space when that folder is gone |
 | `GET` | `/api/spaces/{id}/board` | the lists and cards of one space |
-| `GET` | `/api/agenda` | open cards due within a week or in hand, on every board, whether the diary has today, and its entries `on_this_day` in earlier years |
+| `GET` | `/api/agenda` | open cards due within a week or in hand, on every board, whether the diary has today, its entries `on_this_day` in earlier years, and `today` in `WORKSPACE_TIMEZONE`, with its bounds |
 | `GET` | `/api/diary/days?month=2026-10` | the diary's entries in a month, each with its local `day` |
 | `GET` | `/api/diary/around/{id}` | the entries before and after a diary entry, by date |
 | `GET` | `/api/nodes/{id}/templates` | the templates of the space the node is in |
diff --git a/docs/wiki/Boards-and-Agenda.md b/docs/wiki/Boards-and-Agenda.md
index 20c979e..7b4652d 100644
--- a/docs/wiki/Boards-and-Agenda.md
+++ b/docs/wiki/Boards-and-Agenda.md
@@ -107,7 +107,9 @@ does not make a second copy. The board and the agenda show the rule as
 | `T` | today's diary entry |
 | `t`, `q`, `Esc` | close |
 
-The agenda opens by itself once a day when something is late or due. The bar
+The agenda opens by itself once a day when something is late or due. "Today"
+is the day in `WORKSPACE_TIMEZONE`, the same as for the mails, so a browser in
+another timezone groups the cards the same way. The bar
 shows the `late` and `today` counts whenever either is above zero. With mail
 set up, cards due today are mailed in the morning too; see
 [Backup and mail](Backup-and-Mail.md#mail).
diff --git a/scripts/screenshots.ts b/scripts/screenshots.ts
index 19ec9d3..ea03368 100644
--- a/scripts/screenshots.ts
+++ b/scripts/screenshots.ts
@@ -356,7 +356,7 @@ await send('Page.enable')
 await send('Network.enable')
 // The agenda opens itself once a day; here it opens when asked.
 await send('Page.addScriptToEvaluateOnNewDocument', {
-  source: `localStorage.setItem('diary:agenda-seen', new Date().toDateString())`,
+  source: `localStorage.setItem('diary:agenda-seen', new Intl.DateTimeFormat('en-CA', { timeZone: 'Europe/Berlin' }).format(new Date()))`,
 })
 
 await viewport(1440, 900)
diff --git a/src/routes/boards.rs b/src/routes/boards.rs
index 032be50..4c9da81 100644
--- a/src/routes/boards.rs
+++ b/src/routes/boards.rs
@@ -157,6 +157,21 @@ pub struct Agenda {
     pub diary_today: Option<bool>,
     /// Diary entries from this day in earlier years, the latest year first.
     pub on_this_day: Vec<crate::routes::diary::Entry>,
+    /// Today in the configured timezone, which is the day the cards are due
+    /// on and the mails are sent by — not the browser's, which may be
+    /// somewhere else, and not 24 hours long when the clocks change.
+    pub today: AgendaDay,
+}
+
+#[derive(Serialize)]
+pub struct AgendaDay {
+    /// `2026-10-21`.
+    pub date: String,
+    /// When today starts and ends, in Unix seconds.
+    pub start: i64,
+    pub end: i64,
+    /// The end of the seventh day after today: what is due before it is this week.
+    pub week_end: i64,
 }
 
 #[derive(Serialize)]
@@ -189,10 +204,19 @@ pub async fn agenda(_: Session, State(state): State<AppState>) -> AppResult<Json
     };
     let on_this_day = crate::routes::diary::on_this_day(&state.db, tz, crate::now()).await?;
 
+    let day = crate::notify::local_day(tz, crate::now());
+    let (start, end) = crate::notify::day_bounds(tz, day);
+    let (_, week_end) = crate::notify::day_bounds(tz, day + chrono::Duration::days(AGENDA_DAYS));
     Ok(Json(Agenda {
         cards,
         diary_today,
         on_this_day,
+        today: AgendaDay {
+            date: day.format("%Y-%m-%d").to_string(),
+            start,
+            end,
+            week_end,
+        },
     }))
 }
 
@@ -1405,4 +1429,36 @@ mod tests {
         let ids = [1, 2, 3];
         assert_eq!(reordered(&ids, 2, 1), vec![1, 2, 3]);
     }
+
+    /// The agenda says which day it counts as today, in the workspace's
+    /// timezone, with the bounds the browser groups the cards by.
+    #[tokio::test]
+    async fn the_agenda_says_what_today_is() {
+        let state = crate::routes::tests::state_in(".".into()).await;
+        let agenda = super::agenda(
+            crate::auth::Session { id: "test".into() },
+            axum::extract::State(state.clone()),
+        )
+        .await
+        .unwrap()
+        .0;
+        let tz = state.config.mail.timezone;
+        let now = crate::now();
+        let day = &agenda.today;
+        assert_eq!(
+            day.date,
+            crate::notify::local_day(tz, now)
+                .format("%Y-%m-%d")
+                .to_string()
+        );
+        assert!(
+            day.start <= now && now < day.end,
+            "{} {} {}",
+            day.start,
+            now,
+            day.end
+        );
+        // Seven more local days, each 23 to 25 hours long.
+        assert!((day.week_end - day.end - 7 * 86400).abs() <= 3600);
+    }
 }
diff --git a/web/src/lib/api.ts b/web/src/lib/api.ts
index 0acfdfa..ee65a86 100644
--- a/web/src/lib/api.ts
+++ b/web/src/lib/api.ts
@@ -194,6 +194,8 @@ export interface Agenda {
   diary_today: boolean | null
   /** Diary entries from this day in earlier years, the latest year first. */
   on_this_day: DiaryEntry[]
+  /** Today in the workspace's timezone, which is what due dates are counted in. */
+  today: { date: string; start: number; end: number; week_end: number } | null
 }
 
 /** A diary entry, by the local day it is about. */
diff --git a/web/src/lib/store.svelte.ts b/web/src/lib/store.svelte.ts
index 8a974a8..85571e0 100644
--- a/web/src/lib/store.svelte.ts
+++ b/web/src/lib/store.svelte.ts
@@ -299,7 +299,7 @@ class Workspace {
    * What is due or in hand on every board, kept loaded all the time: the bar
    * counts from it, so what is late is in sight without going to look.
    */
-  agenda = $state<Agenda>({ cards: [], diary_today: null, on_this_day: [] })
+  agenda = $state<Agenda>({ cards: [], diary_today: null, on_this_day: [], today: null })
   agendaCursor = $state(0)
 
   /** `C`: the day the calendar's cursor is on, `2026-10-20`, and its month's entries. */
@@ -386,16 +386,18 @@ class Workspace {
     return this.list?.cards[this.cardCursor]
   }
 
-  /** The agenda in the order it is drawn and walked, bucketed by urgency. */
+  /**
+   * The agenda in the order it is drawn and walked, bucketed by urgency. The
+   * day is the server's, in the workspace's timezone, so a browser on a trip
+   * groups the cards the way the morning mail does.
+   */
   get agendaGroups(): { key: 'overdue' | 'today' | 'week' | 'doing'; cards: AgendaCard[] }[] {
-    const midnight = new Date()
-    midnight.setHours(0, 0, 0, 0)
-    const start = Math.floor(midnight.getTime() / 1000)
+    const { start, end, week_end } = this.agenda.today ?? { start: 0, end: 0, week_end: 0 }
     const groups = { overdue: [] as AgendaCard[], today: [] as AgendaCard[], week: [] as AgendaCard[], doing: [] as AgendaCard[] }
     for (const card of this.agenda.cards) {
       if (card.due_at !== null && card.due_at < start) groups.overdue.push(card)
-      else if (card.due_at !== null && card.due_at < start + 86400) groups.today.push(card)
-      else if (card.due_at !== null && card.due_at < start + 8 * 86400) groups.week.push(card)
+      else if (card.due_at !== null && card.due_at < end) groups.today.push(card)
+      else if (card.due_at !== null && card.due_at < week_end) groups.week.push(card)
       else if (card.role === 'doing') groups.doing.push(card)
     }
     return (['overdue', 'today', 'week', 'doing'] as const).map((key) => ({ key, cards: groups[key] }))
@@ -1306,8 +1308,8 @@ class Workspace {
    * point is to be told, not to have to remember to ask.
    */
   async openAgendaIfDue() {
-    const today = new Date().toDateString()
-    if (localStorage.getItem('diary:agenda-seen') === today) return
+    const today = this.agenda.today?.date
+    if (!today || localStorage.getItem('diary:agenda-seen') === today) return
     const { late, today: due } = this.dueCounts
     if (late + due === 0) return
     localStorage.setItem('diary:agenda-seen', today)