diff --git a/apps/web/a11y/planner.a11y.ts b/apps/web/a11y/planner.a11y.ts
new file mode 100644
index 0000000..5e486ee
--- /dev/null
+++ b/apps/web/a11y/planner.a11y.ts
@@ -0,0 +1,128 @@
+import AxeBuilder from '@axe-core/playwright';
+import { scanWcag22AaViolations } from '@davidvornholt/a11y-testing/axe';
+import { expect, test as it, test } from '@playwright/test';
+import { defaultSettings } from '../src/shared/hooks/use-settings-schema';
+import { createSessionCookies } from './auth-fixture';
+
+const timetable = ['monday', 'tuesday', 'wednesday', 'thursday', 'friday'].map(
+  (day) => ({
+    day,
+    slots: [{ id: `${day}-1`, subjectId: 'math' }],
+  }),
+);
+const plannerSettings = {
+  ...defaultSettings,
+  subjects: [{ id: 'math', name: 'Math' }],
+  timetable,
+};
+
+for (const timezoneId of ['Europe/Berlin', 'America/Los_Angeles']) {
+  test.describe(timezoneId, () => {
+    it.use({ timezoneId });
+    for (const date of ['2026-09-08T12:00:00', '2025-12-30T12:00:00']) {
+      it(`Tuesday exceptions stay on Tuesday on ${date}`, async ({
+        page,
+        context,
+      }) => {
+        await context.addCookies(await createSessionCookies());
+        await page.clock.setFixedTime(new Date(date));
+        await page.addInitScript((settings) => {
+          localStorage.setItem('papersync-settings', JSON.stringify(settings));
+        }, plannerSettings);
+        await page.goto('/planner');
+        const tuesday = page
+          .getByRole('listitem')
+          .filter({ has: page.getByText('Tue', { exact: true }) });
+        const monday = page
+          .getByRole('listitem')
+          .filter({ has: page.getByText('Mon', { exact: true }) });
+        const exceptionButton = tuesday.getByRole('button');
+        await exceptionButton.click();
+        const dialog = page.getByRole('dialog');
+        await expect(dialog).toContainText('Tuesday');
+        await dialog.getByLabel('Reason (optional)').fill('Museum visit');
+        await dialog.getByRole('button', { name: 'Remove class' }).click();
+        expect(await scanWcag22AaViolations(page)).toEqual([]);
+        await dialog
+          .getByRole('button', { name: 'Add exception', exact: true })
+          .click();
+        await expect(tuesday).toContainText('Museum visit');
+        await expect(tuesday).toContainText('No classes');
+        await expect(monday).not.toContainText('Museum visit');
+        await expect(monday).toContainText('Math');
+        const savedExceptionAccessibility = await new AxeBuilder({ page })
+          .withRules(['label-content-name-mismatch'])
+          .analyze();
+        expect(savedExceptionAccessibility.violations).toEqual([]);
+        await expect(exceptionButton).toHaveAccessibleName(
+          'Edit exception for Tuesday',
+        );
+        await exceptionButton.click();
+        await expect(dialog.getByLabel('Reason (optional)')).toHaveValue(
+          'Museum visit',
+        );
+        await dialog.getByLabel('Reason (optional)').fill('Museum trip');
+        await dialog.getByRole('button', { name: 'Save changes' }).click();
+        await expect(tuesday).toContainText('Museum trip');
+        const { promise: generationHeld, resolve: releaseGeneration } =
+          Promise.withResolvers<void>();
+        let requests = 0;
+        await page.route('**/api/planner', async (route) => {
+          requests += 1;
+          if (requests === 1) {
+            await generationHeld;
+          }
+          const payload = route.request().postDataJSON();
+          expect(payload.timetable).toEqual(
+            timetable.map((day) =>
+              day.day === 'tuesday' ? { ...day, slots: [] } : day,
+            ),
+          );
+          await route.fulfill({
+            contentType: 'application/pdf',
+            body: '%PDF-1.4\n%%EOF',
+          });
+        });
+        await page
+          .getByRole('button', { name: 'Generate PDF', exact: true })
+          .click();
+        await expect(
+          page.getByText('Generating PDF…', { exact: true }),
+        ).toBeVisible();
+        await exceptionButton.click();
+        await dialog
+          .getByLabel('Reason (optional)')
+          .fill('Museum trip, updated');
+        await dialog.getByRole('button', { name: 'Save changes' }).click();
+        const staleResponse = page.waitForResponse('**/api/planner');
+        releaseGeneration();
+        await staleResponse;
+        await expect(
+          page.getByText('Review the schedule, then generate your PDF'),
+        ).toBeVisible();
+        await expect(
+          page.getByRole('button', { name: 'Download', exact: true }),
+        ).toHaveCount(0);
+        await page
+          .getByRole('button', { name: 'Generate PDF', exact: true })
+          .click();
+        await expect(
+          page.getByRole('button', { name: 'Download', exact: true }),
+        ).toBeVisible();
+        await exceptionButton.click();
+        await dialog
+          .getByRole('button', { name: 'Remove exception', exact: true })
+          .click();
+        await expect(tuesday).not.toContainText('Museum trip');
+        await expect(tuesday).toContainText('Math');
+        await expect(
+          tuesday.getByRole('button', { name: 'Exception for Tuesday' }),
+        ).toBeVisible();
+        await expect(
+          page.getByRole('button', { name: 'Download', exact: true }),
+        ).toHaveCount(0);
+        expect(await scanWcag22AaViolations(page)).toEqual([]);
+      });
+    }
+  });
+}
diff --git a/apps/web/src/features/planner/hooks/use-planner.ts b/apps/web/src/features/planner/hooks/use-planner.ts
index 75538e4..8a099e4 100644
--- a/apps/web/src/features/planner/hooks/use-planner.ts
+++ b/apps/web/src/features/planner/hooks/use-planner.ts
@@ -1,7 +1,7 @@
 'use client';
 
 import { Data, Effect } from 'effect';
-import { useCallback, useState } from 'react';
+import { useCallback, useRef, useState } from 'react';
 import { getWeekDateRange, getWeekId } from '@/shared/planner/week';
 import type { Subject, WeekId } from '@/shared/types/schemas';
 import { downloadPlannerPdf } from '../services/generator';
@@ -83,22 +83,31 @@ export const usePlanner = (initialWeekId?: WeekId): UsePlannerReturn => {
   const dateRange = getWeekDateRange(weekId);
 
   const [state, setState] = useState<PlannerState>({ status: 'idle' });
+  const revisionRef = useRef(0);
 
   const generate = useCallback(
     (
       subjects: ReadonlyArray<Subject>,
       timetable: ReadonlyArray<TimetableDay>,
     ): Promise<void> => {
+      revisionRef.current += 1;
+      const revision = revisionRef.current;
       setState({ status: 'generating' });
       return Effect.runPromise(
         fetchPdfEffect(weekId, subjects, timetable).pipe(
           Effect.tap((blob) =>
-            Effect.sync(() => setState({ status: 'generated', blob })),
+            Effect.sync(() => {
+              if (revision === revisionRef.current) {
+                setState({ status: 'generated', blob });
+              }
+            }),
           ),
           Effect.catchAll((error) =>
-            Effect.sync(() =>
-              setState({ status: 'error', error: error.message }),
-            ),
+            Effect.sync(() => {
+              if (revision === revisionRef.current) {
+                setState({ status: 'error', error: error.message });
+              }
+            }),
           ),
           Effect.asVoid,
         ),
@@ -125,6 +134,7 @@ export const usePlanner = (initialWeekId?: WeekId): UsePlannerReturn => {
   }, [state]);
 
   const reset = useCallback((): void => {
+    revisionRef.current += 1;
     setState({ status: 'idle' });
   }, []);
 
diff --git a/apps/web/src/features/planner/screens/components/exception-editor-modal.tsx b/apps/web/src/features/planner/screens/components/exception-editor-modal.tsx
index 5fc6c4d..cc9f7ed 100644
--- a/apps/web/src/features/planner/screens/components/exception-editor-modal.tsx
+++ b/apps/web/src/features/planner/screens/components/exception-editor-modal.tsx
@@ -3,7 +3,8 @@
 import { Button } from '@papersync/ui/button';
 import { useEffect, useId, useState } from 'react';
 import { Modal } from '@/shared/components/modal';
-import type { DayOfWeek, ISODate, Subject } from '@/shared/types/schemas';
+import { getIsoDate } from '@/shared/planner/week';
+import type { DayOfWeek, Subject } from '@/shared/types/schemas';
 import type { ScheduleException } from '../planner-screen-types';
 import { ExceptionSlotEditor } from './exception-slot-editor';
 
@@ -51,7 +52,7 @@ export const ExceptionEditorModal = ({
     <Modal
       isOpen={isOpen}
       onClose={onClose}
-      title={exception ? 'Edit Exception' : 'Add Exception'}
+      title={exception ? 'Edit exception' : 'Add exception'}
       description={`Modify the schedule for ${dateStr}`}
       size="md"
       footer={
@@ -73,7 +74,7 @@ export const ExceptionEditorModal = ({
           </Button>
           <Button
             onClick={() => {
-              const isoDate = date.toISOString().split('T')[0] as ISODate;
+              const isoDate = getIsoDate(date);
               onSave({
                 date: isoDate,
                 dayOfWeek,
diff --git a/apps/web/src/features/planner/screens/components/exception-slot-editor.tsx b/apps/web/src/features/planner/screens/components/exception-slot-editor.tsx
index 837d01f..e569f97 100644
--- a/apps/web/src/features/planner/screens/components/exception-slot-editor.tsx
+++ b/apps/web/src/features/planner/screens/components/exception-slot-editor.tsx
@@ -45,6 +45,7 @@ export const ExceptionSlotEditor = ({
               {String(index + 1).padStart(2, '0')}
             </span>
             <Select
+              aria-label={`Exception class ${index + 1}`}
               value={slot.subjectId}
               onChange={(e) => onChangeSlot(slot.id, e.target.value)}
               className="min-w-0 flex-1 text-[14px]"
diff --git a/apps/web/src/features/planner/screens/components/week-schedule-overview.tsx b/apps/web/src/features/planner/screens/components/week-schedule-overview.tsx
index 21e37bb..9a10179 100644
--- a/apps/web/src/features/planner/screens/components/week-schedule-overview.tsx
+++ b/apps/web/src/features/planner/screens/components/week-schedule-overview.tsx
@@ -40,6 +40,9 @@ export const WeekScheduleOverview = ({
 
         const exception = exceptions.find((entry) => entry.date === isoDate);
         const hasException = exception !== undefined;
+        const exceptionAction = hasException
+          ? { text: 'Edit', label: 'Edit exception' }
+          : { text: 'Exception', label: 'Exception' };
         const slots = hasException
           ? exception.slots
           : (daySchedule?.slots ?? []);
@@ -103,9 +106,10 @@ export const WeekScheduleOverview = ({
                   variant="ghost"
                   size="sm"
                   onClick={() => onEditException(dayDate, day)}
+                  aria-label={`${exceptionAction.label} for ${dayDate.toLocaleDateString('en-US', { weekday: 'long' })}`}
                   className={hasException ? 'text-warning' : ''}
                 >
-                  {hasException ? 'Edit' : 'Exception'}
+                  {exceptionAction.text}
                 </Button>
               </div>
             </div>
diff --git a/apps/web/src/features/planner/screens/planner-screen-helpers.ts b/apps/web/src/features/planner/screens/planner-screen-helpers.ts
index 481d359..38a9dee 100644
--- a/apps/web/src/features/planner/screens/planner-screen-helpers.ts
+++ b/apps/web/src/features/planner/screens/planner-screen-helpers.ts
@@ -1,5 +1,6 @@
 import type { TimetableDay } from '@/shared/hooks/use-settings-schema';
-import type { DayOfWeek, ISODate, Subject } from '@/shared/types/schemas';
+import { getIsoDate } from '@/shared/planner/week';
+import type { DayOfWeek, Subject } from '@/shared/types/schemas';
 import type { PlannerState } from '../hooks/use-planner';
 import type {
   PreviewPanelState,
@@ -72,7 +73,7 @@ export const applyExceptionsToTimetable = (
       const dayIndex = WEEKDAYS.indexOf(daySchedule.day);
       const dayDate = new Date(weekStartDate);
       dayDate.setDate(weekStartDate.getDate() + dayIndex);
-      const isoDate = dayDate.toISOString().split('T')[0] as ISODate;
+      const isoDate = getIsoDate(dayDate);
 
       const exception = exceptions.find((entry) => entry.date === isoDate);
       if (!exception) {
@@ -97,7 +98,7 @@ export const getExceptionForDate = (
   exceptions: ReadonlyArray<ScheduleException>,
   date: Date,
 ): ScheduleException | null => {
-  const isoDate = date.toISOString().split('T')[0] as ISODate;
+  const isoDate = getIsoDate(date);
   return exceptions.find((entry) => entry.date === isoDate) ?? null;
 };
 
diff --git a/apps/web/src/features/planner/screens/use-planner-screen.ts b/apps/web/src/features/planner/screens/use-planner-screen.ts
index c4a5e90..14b28b4 100644
--- a/apps/web/src/features/planner/screens/use-planner-screen.ts
+++ b/apps/web/src/features/planner/screens/use-planner-screen.ts
@@ -3,8 +3,8 @@
 import { useMemo, useState } from 'react';
 import { useToast } from '@/shared/components/use-toast';
 import { useSettings } from '@/shared/hooks/use-settings';
-import { getWeekId, getWeekStartDate } from '@/shared/planner/week';
-import type { DayOfWeek, ISODate, WeekId } from '@/shared/types/schemas';
+import { getIsoDate, getWeekId, getWeekStartDate } from '@/shared/planner/week';
+import type { DayOfWeek, WeekId } from '@/shared/types/schemas';
 import { usePlanner } from '../hooks/use-planner';
 import {
   applyExceptionsToTimetable,
@@ -71,6 +71,7 @@ export const usePlannerScreen = () => {
     exceptionData: Omit<ScheduleException, 'id'>,
   ): void => {
     setExceptions((prev) => upsertException(prev, exceptionData));
+    planner.reset();
     addToast('Schedule exception saved', 'success');
   };
 
@@ -79,10 +80,9 @@ export const usePlannerScreen = () => {
       return;
     }
 
-    const isoDate = exceptionEditingDate.date
-      .toISOString()
-      .split('T')[0] as ISODate;
+    const isoDate = getIsoDate(exceptionEditingDate.date);
     setExceptions((prev) => prev.filter((entry) => entry.date !== isoDate));
+    planner.reset();
     addToast('Exception removed', 'info');
   };