test(utils): check boundary robustness of time normalization (Variation 2)

- Add tests for extreme timezone offsets (UTC+5:30, UTC+14, UTC-12)
- Verify timestamps convert cleanly to target offset without calendar shifting
- Cover year-end boundary cases for UTC+14 and UTC-11

Closes JhaSourav07#1559

Author: Priti-007

utils/time.test.ts

@@ -233,3 +233,53 @@ describe('getSecondsUntilUTCMidnight — sliding window boundary robustness', ()
     }
   });
 });
+
+describe('getSecondsUntilMidnightInTimezone — extreme timezone offset boundary robustness', () => {
+  beforeEach(() => {
+    vi.useFakeTimers();
+  });
+
+  afterEach(() => {
+    vi.useRealTimers();
+  });
+
+  it('converts timestamp cleanly to target offset without calendar shifting (UTC+5:30)', () => {
+    // UTC 2024-06-15T18:30:00Z = 2024-06-16T00:00:00 in Asia/Kolkata (UTC+5:30)
+    // So exactly at local midnight → 86400 seconds remaining
+    vi.setSystemTime(new Date('2024-06-15T18:30:00.000Z'));
+
+    expect(getSecondsUntilMidnightInTimezone('Asia/Kolkata')).toBe(86400);
+  });
+
+  it('converts timestamp cleanly to target offset without calendar shifting (UTC+14)', () => {
+    // UTC 2024-06-14T10:00:00Z = 2024-06-15T00:00:00 in Pacific/Kiritimati (UTC+14)
+    // Exactly local midnight → 86400 seconds remaining, no date shift
+    vi.setSystemTime(new Date('2024-06-14T10:00:00.000Z'));
+
+    expect(getSecondsUntilMidnightInTimezone('Pacific/Kiritimati')).toBe(86400);
+  });
+
+  it('converts timestamp cleanly to target offset without calendar shifting (UTC-12)', () => {
+    // UTC 2024-06-15T12:00:00Z = 2024-06-15T00:00:00 in Etc/GMT+12 (UTC-12)
+    // Exactly local midnight → 86400 seconds remaining, no date shift
+    vi.setSystemTime(new Date('2024-06-15T12:00:00.000Z'));
+
+    expect(getSecondsUntilMidnightInTimezone('Etc/GMT+12')).toBe(86400);
+  });
+
+  it('handles a timestamp near year-end boundary without calendar shifting (UTC+14)', () => {
+    // UTC 2023-12-31T10:00:00Z = 2024-01-01T00:00:00 in Pacific/Kiritimati
+    // Crosses year boundary cleanly → 86400 seconds remaining
+    vi.setSystemTime(new Date('2023-12-31T10:00:00.000Z'));
+
+    expect(getSecondsUntilMidnightInTimezone('Pacific/Kiritimati')).toBe(86400);
+  });
+
+  it('handles a timestamp near year-end boundary without calendar shifting (UTC-11)', () => {
+    // UTC 2024-01-01T11:00:00Z = 2024-01-01T00:00:00 in Pacific/Midway (UTC-11)
+    // Crosses year boundary cleanly → 86400 seconds remaining
+    vi.setSystemTime(new Date('2024-01-01T11:00:00.000Z'));
+
+    expect(getSecondsUntilMidnightInTimezone('Pacific/Midway')).toBe(86400);
+  });
+});