Question 1

How does the time zone converter handle daylight saving time?

Accepted Answer

Every offset is computed from the browser's built-in IANA time zone database through Intl.DateTimeFormat. For the exact comparison moment, the converter reads the zone's wall-clock fields, rebuilds them as a UTC instant and subtracts the real instant, so the offset reflects whatever daylight saving rule is active at that date — including the weeks each region switches.

Question 2

What is the formula for converting one time zone to another?

Accepted Answer

Convert to UTC first, then to the target zone: targetTime = momentUTC + targetOffset, where momentUTC = localTime − localOffset. Offsets are expressed in minutes, so a 5:30 zone such as Asia/Kolkata is stored as +330 minutes rather than a fractional hour. The converter applies this formula independently for every selected city against the same shared moment.

Question 3

Why do some cities differ by 30 or 45 minutes?

Accepted Answer

Not every zone sits on a whole-hour boundary. India is UTC+05:30, Nepal is UTC+05:45 and parts of Australia use UTC+09:30. Because offsets are kept in minutes, these half- and quarter-hour zones convert exactly instead of being rounded to the nearest hour.

Question 4

How do leap years affect time calculations?

Accepted Answer

A Gregorian year is a leap year when it is divisible by 4, except centuries that are not divisible by 400 — so 2000 was a leap year but 1900 was not. A leap year has 366 days (31,622,400 seconds) instead of 365 (31,536,000 seconds). The extra day keeps the calendar aligned with Earth's orbit, and it never shifts a time zone offset because offsets are defined against UTC, not against the calendar.

Question 5

Does the converter need a network connection?

Accepted Answer

No. All offsets come from the IANA data already shipped with your browser, so conversions are instant, private and work offline. Nothing about the cities you compare is sent anywhere.

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