fix(web): preserve timezone when changing timestamp (Closes #25354) (#27095)

web/src/lib/modals/AssetChangeDateModal.spec.ts

@@ -0,0 +1,67 @@
+import { getAnimateMock } from '$lib/__mocks__/animate.mock';
+import { getIntersectionObserverMock } from '$lib/__mocks__/intersection-observer.mock';
+import { getVisualViewportMock } from '$lib/__mocks__/visual-viewport.mock';
+import { fireEvent, render, screen, waitFor } from '@testing-library/svelte';
+import { DateTime } from 'luxon';
+import { afterAll, beforeEach, describe, expect, test, vi } from 'vitest';
+import AssetChangeDateModal from './AssetChangeDateModal.svelte';
+
+describe('AssetChangeDateModal component', () => {
+  const initialDate = DateTime.fromISO('2026-03-19T23:31:30.112');
+  const initialTimeZone = 'Europe/Lisbon';
+  const onClose = vi.fn();
+
+  const getDateInput = async () => (await screen.findByDisplayValue('2026-03-19T23:31:30.112')) as HTMLInputElement;
+  const getTimeZoneInput = () => screen.getByRole('combobox', { name: /timezone/i }) as HTMLInputElement;
+
+  beforeEach(() => {
+    vi.stubGlobal('IntersectionObserver', getIntersectionObserverMock());
+    vi.stubGlobal('visualViewport', getVisualViewportMock());
+    vi.resetAllMocks();
+    Element.prototype.animate = getAnimateMock();
+  });
+
+  afterAll(async () => {
+    await waitFor(() => {
+      expect(document.body.style.pointerEvents).not.toBe('none');
+    });
+  });
+
+  test('preserves the selected timezone when changing the datetime', async () => {
+    render(AssetChangeDateModal, {
+      props: {
+        initialDate,
+        initialTimeZone,
+        timezoneInput: true,
+        asset: { id: 'asset-id' } as never,
+        onClose,
+      },
+    });
+
+    const timezoneInput = getTimeZoneInput();
+    const datetimeInput = await getDateInput();
+
+    const initialTimezoneValue = timezoneInput.value;
+
+    await fireEvent.focus(timezoneInput);
+    await fireEvent.input(timezoneInput, { target: { value: 'Pacific/Pitcairn' } });
+
+    const option = await screen.findByText(/Pacific\/Pitcairn/i);
+    await fireEvent.click(option);
+
+    expect(timezoneInput.value).toBe('Pacific/Pitcairn (-08:00)');
+    expect(timezoneInput.value).not.toBe(initialTimezoneValue);
+
+    const beforeDatetime = datetimeInput.value;
+
+    await fireEvent.input(datetimeInput, {
+      target: { value: '2026-03-19T23:31:31.113' },
+    });
+    await fireEvent.change(datetimeInput, {
+      target: { value: '2026-03-19T23:31:31.113' },
+    });
+
+    expect(datetimeInput.value).not.toBe(beforeDatetime);
+    expect(timezoneInput.value).toBe('Pacific/Pitcairn (-08:00)');
+  });
+});

web/src/lib/modals/AssetChangeDateModal.svelte

@@ -23,10 +23,7 @@
   let selectedDate = $state(initialDate.toFormat("yyyy-MM-dd'T'HH:mm:ss.SSS"));
   const timezones = $derived(getTimezones(selectedDate));
 
-  // svelte-ignore state_referenced_locally
-  let lastSelectedTimezone = $state(getPreferredTimeZone(initialDate, initialTimeZone, timezones));
-  // the offsets (and validity) for time zones may change if the date is changed, which is why we recompute the list
-  let selectedOption = $derived(getPreferredTimeZone(initialDate, initialTimeZone, timezones, lastSelectedTimezone));
+  let selectedOption = $state(getPreferredTimeZone(initialDate, initialTimeZone, getTimezones(selectedDate)));
 
   const onSubmit = async () => {
     if (!date.isValid || !selectedOption) {
@@ -45,6 +42,12 @@
     }
   };
 
+  const updateSelectedDate = (value: string) => {
+    selectedDate = value;
+
+    selectedOption = getPreferredTimeZone(initialDate, initialTimeZone, getTimezones(value), selectedOption);
+  };
+
   // when changing the time zone, assume the configured date/time is meant for that time zone (instead of updating it)
   const date = $derived(DateTime.fromISO(selectedDate, { zone: selectedOption?.value, setZone: true }));
 </script>
@@ -59,7 +62,12 @@
   size="small"
 >
   <Label for="datetime" class="block mb-1">{$t('date_and_time')}</Label>
-  <DateInput class="immich-form-input w-full mb-2" id="datetime" type="datetime-local" bind:value={selectedDate} />
+  <DateInput
+    class="immich-form-input w-full mb-2"
+    id="datetime"
+    type="datetime-local"
+    bind:value={() => selectedDate, updateSelectedDate}
+  />
   {#if timezoneInput}
     <div class="w-full">
       <Combobox bind:selectedOption label={$t('timezone')} options={timezones} placeholder={$t('search_timezone')} />