diff --git a/src/app/features/room/ScheduleMessageModal.tsx b/src/app/features/room/ScheduleMessageModal.tsx
index 0bdb872b8..2ad8fa487 100644
--- a/src/app/features/room/ScheduleMessageModal.tsx
+++ b/src/app/features/room/ScheduleMessageModal.tsx
@@ -20,7 +20,12 @@ import { IContent } from 'matrix-js-sdk';
 import { useTimestampFormatter } from '../../hooks/useTimestampFormatter';
 import { useMatrixClient } from '../../hooks/useMatrixClient';
 import { stopPropagation } from '../../utils/keyboard';
-import { scheduleMessage } from '../../utils/scheduledMessages';
+import {
+  describeScheduleError,
+  MAX_SCHEDULE_AHEAD_MS,
+  scheduleMessage,
+  SCHEDULE_TOO_FAR_TEXT,
+} from '../../utils/scheduledMessages';
 import { useModalStyle } from '../../hooks/useModalStyle';
 import {
   toLocalDate,
@@ -121,7 +126,13 @@ export function ScheduleMessageModal({
       return;
     }
     const diffMs = sendAt.getTime() - Date.now();
-    if (diffMs < 60_000) {
+    // [Gitea #275] Say so as soon as a too-late time is picked, not on submit.
+    const tooFar = diffMs > MAX_SCHEDULE_AHEAD_MS;
+    setError((e) => {
+      if (tooFar) return SCHEDULE_TOO_FAR_TEXT;
+      return e === SCHEDULE_TOO_FAR_TEXT ? null : e;
+    });
+    if (diffMs < 60_000 || tooFar) {
       setPreview(null);
       return;
     }
@@ -149,6 +160,10 @@ export function ScheduleMessageModal({
       setError('Scheduled time must be at least 1 minute in the future.');
       return;
     }
+    if (diffMs > MAX_SCHEDULE_AHEAD_MS) {
+      setError(SCHEDULE_TOO_FAR_TEXT);
+      return;
+    }
     if (!messageText.trim()) {
       setError('Please enter a message to schedule.');
       return;
@@ -162,7 +177,7 @@ export function ScheduleMessageModal({
       onScheduled(delayId, sendAt.getTime(), content);
       onClose();
     } catch (err) {
-      setError(err instanceof Error ? err.message : 'Failed to schedule message.');
+      setError(describeScheduleError(err));
       setSubmitting(false);
     }
   };
@@ -247,6 +262,8 @@ export function ScheduleMessageModal({
                     <input
                       id="schedule-date"
                       type="date"
+                      min={toLocalDate(new Date())}
+                      max={toLocalDate(new Date(Date.now() + MAX_SCHEDULE_AHEAD_MS))}
                       value={dateValue}
                       onChange={(e) => setDateValue(e.target.value)}
                       style={pickerInputStyle(color, config)}
@@ -294,7 +311,8 @@ export function ScheduleMessageModal({
                   </Box>
                 </Box>
               ) : (
-                (dateValue || timeValue) && (
+                (dateValue || timeValue) &&
+                error !== SCHEDULE_TOO_FAR_TEXT && (
                   <Text size="T200" style={{ color: color.Critical.Main }}>
                     Must be at least 1 minute in the future
                   </Text>
diff --git a/src/app/utils/scheduledMessages.test.ts b/src/app/utils/scheduledMessages.test.ts
index c3328fd5f..45c2e7fb3 100644
--- a/src/app/utils/scheduledMessages.test.ts
+++ b/src/app/utils/scheduledMessages.test.ts
@@ -179,3 +179,15 @@ test('groupScheduledByRoom: groups and sorts by sendAt', () => {
   );
   assert.equal(g.get('!2')?.length, 1);
 });
+
+test('[#275] the server limit maps to friendly text; other errors keep theirs', async () => {
+  const { describeScheduleError, SCHEDULE_TOO_FAR_TEXT, MAX_SCHEDULE_AHEAD_MS } =
+    await import('./scheduledMessages');
+  assert.equal(MAX_SCHEDULE_AHEAD_MS, 86_400_000);
+  const tooLarge = Object.assign(new Error('The requested delay (172800000ms) exceeds…'), {
+    errcode: 'ORG.MATRIX.MSC4140_DELAY_TOO_LARGE',
+  });
+  assert.equal(describeScheduleError(tooLarge), SCHEDULE_TOO_FAR_TEXT);
+  assert.equal(describeScheduleError(new Error('Boom')), 'Boom');
+  assert.equal(describeScheduleError('nope'), 'Failed to schedule message.');
+});
diff --git a/src/app/utils/scheduledMessages.ts b/src/app/utils/scheduledMessages.ts
index a8acde312..0b76e1ed9 100644
--- a/src/app/utils/scheduledMessages.ts
+++ b/src/app/utils/scheduledMessages.ts
@@ -1,6 +1,22 @@
 import { IContent, MatrixClient, Method } from 'matrix-js-sdk';
 import type { ScheduledMessage } from '../state/scheduledMessages';
 
+/**
+ * [Gitea #275] Production Synapse caps delayed events at
+ * `max_event_delay_duration: 24h`; a later time is rejected with
+ * ORG.MATRIX.MSC4140_DELAY_TOO_LARGE. The dialog enforces the same limit and
+ * the server's error maps to the same text, in case the limit changes.
+ */
+export const MAX_SCHEDULE_AHEAD_MS = 24 * 60 * 60 * 1000;
+export const SCHEDULE_TOO_FAR_TEXT = 'You can schedule up to 24 hours ahead.';
+
+/** A user-facing sentence for a failed schedule. */
+export const describeScheduleError = (err: unknown): string => {
+  const errcode = (err as { errcode?: unknown } | null)?.errcode;
+  if (errcode === 'ORG.MATRIX.MSC4140_DELAY_TOO_LARGE') return SCHEDULE_TOO_FAR_TEXT;
+  return err instanceof Error ? err.message : 'Failed to schedule message.';
+};
+
 /**
  * Schedule a message via MSC4140 (delayed messages).
  * Synapse implementation: pass org.matrix.msc4140.delay on the standard