Time Zone Converter

Put in a time and a place, add as many other places as you like, and see the same moment from all of them. The grid at the bottom shows a whole day at once, which is the quickest way to find an hour that does not require somebody to get up at four.

The offset is not a property of a place

London to New York, 2026

8 March      5 hours
9 March      4 hours
28 March     4 hours
30 March     5 hours
24 October   5 hours
26 October   4 hours
2 November   5 hours

The gap is usually five. For three weeks in
spring and one in autumn it is four, because the
two countries change on different dates.

New York is five hours behind London, except when it is four. The United States moves its clocks on the second Sunday in March and the European Union on the last Sunday in March, so for about three weeks every spring the usual answer is wrong by an hour. It happens again in autumn, for a week, in the other direction.

This is why the conversion here is always done for a specific date, and not by looking up a fixed difference. A converter that does not ask you which day you mean is guessing, and it guesses wrong roughly a month a year.

The hour that does not exist

29 March 2026, London

00:59:59  ->  01:00:00 does not happen
              the clock reads 02:00:00

01:30 that morning is not a time. Any system
asked to store it has to do something, and what
it does is rarely written down anywhere.

When the clocks go forward, an hour is skipped. Every wall clock reading in that hour names no instant at all. Ask for 01:30 in London on the morning of 29 March 2026 and there is no correct answer, only a choice about what to do instead.

Most software picks something silently. This says so, and shows you the moment the clocks jumped to, which is what a calendar would do with an event you scheduled there.

The hour that happens twice

25 October 2026, London

01:30 BST  =  00:30 UTC
01:30 GMT  =  01:30 UTC

Both are real, an hour apart, and both print as
"01:30". A log file from that hour cannot be put
in order without knowing which was which.

The other end of the year is worse, because nothing looks wrong. When the clocks go back, the hour from 01:00 to 02:00 is lived through twice, and both passes print identically. A timestamp of 01:30 on that morning is genuinely ambiguous, and an hour of log entries cannot be sorted without more information.

When you land on one of those readings this offers both, labelled with which side of the change they fall on. Storing times in UTC avoids the whole problem and is the reason everybody sensible does it.

Never use the abbreviation

IST  India Standard Time     UTC+05:30
IST  Irish Standard Time     UTC+01:00
IST  Israel Standard Time    UTC+02:00

CST  China, Cuba, and central North America
BST  British Summer Time, and Bangladesh once

Abbreviations are not identifiers. Europe/London
is.

IST means three different things, CST means at least four, and none of them are defined by any standard. They are useful for reading and useless for storing. If you are writing something down that a computer will read back, write the IANA name, which is unique and stable: Europe/London, not GMT or BST.

The copy button here gives you the full ISO 8601 stamp for every place, offset included, which is unambiguous and is what a calendar or an API wants.

Where the zone data comes from

Nothing about zones is shipped with this page. Every offset, every changeover date and every abbreviation is asked of your browser, which carries the IANA time zone database and gets it updated whenever the browser does.

That matters more than it sounds. Countries change their minds: Egypt brought summer time back in 2023, Iran dropped it in 2022, Fiji suspended it in 2021, and Samoa once skipped 30 December altogether to change sides of the date line. Anything with the rules baked in goes stale where nobody can see it.

The meeting grid

Each row is a place and each column is one moment. Reading down a column tells you what everybody would be doing at that hour. Working hours are counted as nine to six and awake as seven in the morning to ten at night, which is a rough cut but enough to see where the overlap is.

Click any column to move the time to it. On a day when the clocks change, one row will show a repeated or skipped hour, which is real and worth seeing instead of smoothing over.