World clock
A list of places and their local times — deceptively simple, and the differences between implementations are entirely in what they do at the edges.
The short answer
A world clock shows the current local time in several places at once, so you can see them side by side instead of converting each one.
The useful ones add the things a bare number leaves out: the date (which often differs), the UTC offset, and whether it is currently day or night there.
What separates a good one from a bad one
The basic function is trivial. The differences are all in the edge cases, and they are exactly the cases that matter when you rely on it.
Half- and quarter-hour zones. India is UTC+5:30, Nepal UTC+5:45, Chatham Islands UTC+13:45. Anything built on whole-hour arithmetic is wrong for a large population.
Daylight saving, on both sides. A clock that stores a fixed offset rather than a zone identifier drifts an hour twice a year, and is wrong for weeks before anyone notices.
The date, not just the time. For anything more than about eight hours away, the date is frequently different. A world clock that shows "07:00" without saying whether that is today or tomorrow has withheld the important half.
Day or night. Knowing it is 3am somewhere is the entire point of checking. Some clocks show it as a sun/moon indicator computed from real coordinates; others guess from the hour, which is wrong at high latitudes in summer.
What to put on it
Fewer places than you think. A list of twenty is unreadable at a glance, which defeats the purpose.
Most people need: home, wherever they currently are if travelling, and the two or three places they deal with regularly. Anything else is better looked up when needed.
Ordering matters more than it seems. Geographic or alphabetical order is tidy and useless; the order you actually think about them in is what makes it scannable.
World clock versus converter
They answer different questions and it is worth being clear which you need.
| Question | Answers | |
|---|---|---|
| World clock | "What time is it there now?" | The present |
| Converter | "If I pick this moment, what time is it there?" | Any moment |
A world clock tells you whether to call. A converter tells you when to schedule. Most real questions need the second one, which is why a clock alone runs out of usefulness quickly.
And the third question — "when are we both awake?" — needs neither. It needs an overlap calculation.
On widgets
The natural home for a world clock is somewhere you see without opening anything — a home screen or lock screen. The whole value is at-a-glance, and an app you have to launch has already lost most of it.
Related: World time clock · When are two cities both awake?
Timezone: World Clock Widget
A world clock, converter and live day/night map for iPhone — 325 cities, offline, no account.
Figures on this page are computed from the IANA time zone database. Last generated 2026-08-18.