Questions
The things people reasonably want to know before trusting a clock, including the version of the time-zone database this build was made against.
Why we publish the tzdata version
Time-zone rules change by government decree several times a year, and software carrying an old database keeps answering fluently with the wrong hour. Egypt reinstated daylight saving in 2023, Türkiye abolished it in 2016, and Kyiv was renamed in 2022. This build was made against tzdata 2025b; your browser carries its own copy, which is what the live clocks read.
Questions
Do the timers keep running if I switch tabs?
Yes. The countdown is measured against a monotonic clock rather than counted in ticks, so a backgrounded tab, a throttled timer or a laptop lid closing does not lose time — when you come back it shows what it should, not what it managed to count.
Do I need an account?
No. Every timer, stopwatch, clock, converter and calendar view here works signed out, with no email and no limit. An account exists for three things only: keeping your saved timers across devices, an alert that reaches you with this tab closed, and subscribing to a calendar.
Where do the time zones come from?
From the IANA time-zone database, through your own browser and our build runtime rather than a list we typed out. This build was made against tzdata 2025b, which names 418 zones. We show that version because a stale time-zone database is a wrong answer that looks completely right.
Why does the difference between two time zones change during the year?
Because countries change their clocks on different dates. The United States moves in March and November, the European Union in the last weekends of March and October, and the southern hemisphere moves the opposite way entirely. For a few weeks each year the usual gap is an hour out, which is when most mis-scheduled calls happen.
What does CST actually mean?
It depends who wrote it, and that is the problem. CST is US Central Time and it is also China Standard Time — fourteen hours apart. IST is India, Ireland and Israel. Every conversion page here names the zone it resolved an abbreviation to, rather than quietly picking one.
Will an alarm go off if I close the tab?
Not on its own — a closed tab runs no code, and any site claiming otherwise is relying on a notification permission you granted earlier. An alert that reaches you with everything closed is scheduled on our servers, and that is the one thing here a membership pays for.
Is my data sent anywhere?
Timers, laps and clock choices are held in your own browser and are not sent to us. If you sign in and save something, it is stored against your account so it can appear on another device — that is the point of saving it.
Does a timer survive a daylight-saving change?
Yes, and the distinction matters. A countdown measures elapsed real time, so a timer set for six hours across a spring-forward still runs six real hours even though the wall clock advances seven. An alarm set for a wall-clock time does the opposite: it fires when the clock says so, which is what you want from an alarm.
Why is Nepal not a whole number of hours?
Because time zones are political rather than geometric. Nepal is UTC+5:45, India UTC+5:30, and the Chatham Islands UTC+12:45. Any converter built on whole hours is wrong for entire countries, which is why nothing here rounds.
Can I use this offline?
The tools themselves are arithmetic in your browser, so once the page has loaded the timer, stopwatch and converter keep working without a connection. Anything that syncs obviously does not.