Time Zone Converter
Pick a date, a time and a place, and see that moment everywhere else. The date matters: the gap between two cities is not the same all year.
Why the date is part of the question
“What is 9am in London, in Delhi?” has two different answers depending on the month. Britain moves its clocks in spring and back in autumn; India never does. So the gap between the two cities is four and a half hours for part of the year and five and a half for the rest.
That is why this page asks for a date and not only a time. A converter that ignores the date is right for about half the year, which is worse than being wrong all of it — you have no reason to check.
It is also why a meeting arranged months ahead can drift. If you agree a recurring call between two countries that change their clocks on different weekends, there will be a fortnight each spring and autumn when somebody arrives an hour out.
Why places, not abbreviations
Short names are not unique, and the confusion is expensive. IST is India Standard Time, Israel Standard Time and Irish Standard Time. CST is used for North America and for China. Two people agreeing a call “at 3pm CST” may be nine hours apart and completely certain they agree.
So everything here uses proper zone names —
Asia/Kolkata, America/New_York. They look
technical and they are exact: each one carries its own full history
of daylight saving changes, which is what makes a conversion for a
particular date possible at all.
The two hours that do not behave
When the clocks go forward, an hour does not exist. 2:30am simply never happens that night, and a time you enter inside that gap has no real answer — every tool quietly picks one.
When they go back, an hour happens twice, so 1:30am is genuinely two different moments. Anything scheduled in those two hours is worth moving by an hour rather than arguing about.
Nothing is sent anywhere
The whole conversion uses the time zone database already inside your browser. No lookup, no server, and it works with the network off — which is exactly when you are most likely to be on a plane wondering what time you land.
Frequently asked questions
Why does it ask for a date as well as a time?
Because daylight saving makes the gap between two places change during the year. London and Delhi are four and a half hours apart in winter and five and a half in summer. Without the date the answer is a coin toss.
What is wrong with saying IST or CST?
They are ambiguous. IST means India, Israel and Ireland; CST is used in both North America and China. Full zone names like Asia/Kolkata cannot be misread, which is why they are used here.
My city is not in the list.
Pick any place in the same zone - the list covers the zones, not every city. If your country changes its clocks on different dates from the one you pick, choose more carefully; otherwise any city in the zone gives the same answer.
What happens at 2:30am on the night the clocks change?
In spring that time does not exist and any answer is a guess. In autumn it happens twice and there are two correct answers. If you are scheduling something, move it an hour away from the changeover.
Does it need the internet?
No. Your browser already carries the full time zone database, including the history of past changes, so everything is worked out on your device.
Is my text sent anywhere?
No. Everything happens in JavaScript inside your own browser. Nothing is uploaded and nothing is saved - close the tab and it is gone.