How many hours apart are two places?

How it works

Every place keeps its clock a set amount ahead of or behind Coordinated Universal Time (UTC), the world's reference time. That amount is the offset: Helsinki is UTC+2 in winter, New York UTC−5, India UTC+5:30. To convert, the time is first turned into UTC and then into each other place's local time.

The rule is local time = UTC + offset. For example, 14:30 in Helsinki on 1 July is 11:30 UTC, because Finnish summer time is UTC+3; New York is UTC−4 in summer, so it is 07:30 there, 7 hours behind. Offsets change when a place starts or ends daylight saving time, and the dates differ between countries: in late March the gap between Finland and New York is 6 hours for about three weeks.

The offsets come from the IANA time zone database, the public record of every region's clock rules, as it is built into your browser. When clocks go back, one hour happens twice and the first one is used; when clocks go forward, one hour does not exist and the time is read with the offset before the change. Future rules can change if a government changes them.