fix(web): timezone dropdown showing "No results" when seconds are set to 00 (#24662)

* Fix timezone dropdown showing "No results" when seconds are set to 00

* remove comments

* add test for #23615

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

@@ -71,6 +71,34 @@ describe('DateSelectionModal component', () => {
     expect(onClose).toHaveBeenCalled();
   });
 
+  test('does not fall back to UTC when datetime-local value has no seconds', async () => {
+    render(AssetSelectionChangeDateModal, {
+      props: { initialDate, initialTimeZone, assets: [], onClose },
+    });
+
+    await fireEvent.input(getDateInput(), { target: { value: '2024-01-01T00:00' } });
+    await fireEvent.blur(getDateInput());
+
+    expect(getTimeZoneInput().value).toBe('Europe/Berlin (+01:00)');
+
+    await fireEvent.focus(getTimeZoneInput());
+    expect(screen.queryByText('no_results')).not.toBeInTheDocument();
+  });
+
+  test('does not fall back to UTC when datetime-local value has no milliseconds', async () => {
+    render(AssetSelectionChangeDateModal, {
+      props: { initialDate, initialTimeZone, assets: [], onClose },
+    });
+
+    await fireEvent.input(getDateInput(), { target: { value: '2024-01-01T00:00:00' } });
+    await fireEvent.blur(getDateInput());
+
+    expect(getTimeZoneInput().value).toBe('Europe/Berlin (+01:00)');
+
+    await fireEvent.focus(getTimeZoneInput());
+    expect(screen.queryByText('no_results')).not.toBeInTheDocument();
+  });
+
   describe('when date is in daylight saving time', () => {
     const dstDate = DateTime.fromISO('2024-07-01');
 

web/src/lib/modals/timezone-utils.ts

@@ -75,8 +75,15 @@ function zoneOptionForDate(zone: string, date: string) {
   // Ignore milliseconds:
   // - milliseconds are not relevant for TZ calculations
   // - browsers strip insignificant .000 making string comparison with milliseconds more fragile.
+  //
+  // Also, some browsers emit `datetime-local` values without seconds when seconds are 00,
+  // e.g. `2024-01-01T00:00` instead of `2024-01-01T00:00:00.000`.
+  // In that case we must compare with minute precision (otherwise every zone looks "invalid").
   const dateInTimezone = DateTime.fromISO(date, { zone });
-  const exists = date.replace(/\.\d+/, '') === dateInTimezone.toFormat("yyyy-MM-dd'T'HH:mm:ss");
+  const withoutMillis = date.replace(/\.\d+/, '');
+  const hasSeconds = /T\d{2}:\d{2}:\d{2}$/.test(withoutMillis);
+  const compareFormat = hasSeconds ? "yyyy-MM-dd'T'HH:mm:ss" : "yyyy-MM-dd'T'HH:mm";
+  const exists = withoutMillis === dateInTimezone.toFormat(compareFormat);
   const valid = dateInTimezone.isValid && exists;
   return {
     value: zone,