How to use the Time Zone Converter
- Enter the date as well as the time — the date determines the offset.
- Choose the source zone and the target zone.
- Read the converted time and the day, which may differ.
- For recurring meetings, re-check the pairing after each daylight saving transition.
How the calculation works
Every zone is defined as an offset from UTC, and many zones change that offset seasonally. Conversion therefore means resolving both zones' offsets on the given date and applying the difference. Offsets are not all whole hours — India runs at UTC+05:30 and Nepal at UTC+05:45 — so mental arithmetic in hours alone will be wrong for a large part of the world.
Daylight saving transitions are the main hazard. The United States and Europe change on different weekends, so for a few weeks each spring and autumn the usual gap between New York and London is an hour out. The southern hemisphere runs the opposite cycle, and some jurisdictions do not observe daylight saving at all, which is why the date is required rather than optional.
Target local time = source local time − source UTC offset + target UTC offset, with offsets resolved for that dateSource: IANA time zone database (tzdata), the reference source for zone offsets and daylight saving rules.
Worked example
A 09:30 meeting in New York on 4 November 2026, for a colleague in Mumbai.
- US daylight saving ends 1 November 2026, so New York is at UTC−05:00.
- 09:30 local = 14:30 UTC.
- Mumbai is UTC+05:30 year-round: 14:30 + 5:30 = 20:00.
20:00 the same day in Mumbai. A week earlier, before the US transition, it would have been 19:00.
Frequently asked questions
Why did my recurring meeting shift by an hour?+
One participant's country changed its daylight saving offset and the other's did not. Anchoring a recurring meeting to one location's local time and letting others recalculate avoids the ambiguity.
Are all time zones whole hours from UTC?+
No. India is UTC+05:30, Nepal UTC+05:45 and parts of Australia UTC+09:30, so offsets in minutes are common enough to matter.
What is the difference between GMT and UTC?+
UTC is the atomic time standard; GMT is a time zone that coincides with it in winter. Britain moves to BST, UTC+1, in summer, so GMT and UK local time are not the same all year.
How should I schedule across many zones?+
Fix the meeting in UTC and publish local equivalents, or use a scheduling tool that resolves zones from tzdata. Both approaches remove the assumption that everyone changes clocks on the same weekend.
Last reviewed August 31, 2026. We review this page whenever the underlying formula, tax year, published rate or standard changes.