Where do the zone names come from?

IANA tz database identifiers like Asia/Seoul or America/Los_Angeles. The browser's Intl.DateTimeFormat handles daylight-saving transitions automatically.

Why does the offset sometimes have :30 or :45?

Several places (India +5:30, Newfoundland −3:30, Nepal +5:45) use offsets that aren't whole hours. The formatter shows them as UTC±H:MM.

How does the difference work?

It's the difference between each zone's offset and your local zone at the reference time. If you're in Seoul (+9) and you compare with Los Angeles (−8 in winter), the diff is −17h.

Does it work offline?

Yes — all calculations use the browser's built-in Intl APIs, no network required after first load.

World Clock

Pick any number of time zones and watch them tick in real time. Each card shows the local time, date, UTC offset, and the difference from your own time zone — handy for scheduling meetings, calling family abroad, or knowing if a remote teammate is asleep. Switch to 12-hour mode or freeze the clocks to a specific reference time to plan ahead.

—

12-hour formatReference time

Asia/Seoul
09:34:36
Fri 21 Aug 2026UTC+9Δ +9h
America/Los_Angeles
17:34:36
Thu 20 Aug 2026UTC-7Δ -7h
Europe/London
01:34:36
Fri 21 Aug 2026UTC+1Δ +1h
Asia/Tokyo
09:34:36
Fri 21 Aug 2026UTC+9Δ +9h

Add a zone

How to use

Pick zones from the suggestion chips below the clocks.
Toggle 12-hour mode if you prefer AM / PM.
Set a reference date / time to see what each zone reads at that moment.
Remove a zone with the × button.

Frequently asked questions

Where do the zone names come from?: IANA tz database identifiers like Asia/Seoul or America/Los_Angeles. The browser's Intl.DateTimeFormat handles daylight-saving transitions automatically.
Why does the offset sometimes have :30 or :45?: Several places (India +5:30, Newfoundland −3:30, Nepal +5:45) use offsets that aren't whole hours. The formatter shows them as UTC±H:MM.
How does the difference work?: It's the difference between each zone's offset and your local zone at the reference time. If you're in Seoul (+9) and you compare with Los Angeles (−8 in winter), the diff is −17h.
Does it work offline?: Yes — all calculations use the browser's built-in Intl APIs, no network required after first load.

Guides on this topic

Working with Time Zones and Unix Timestamps Without Bugs Why time is so hard to get right in software — UTC, Unix timestamps, time zones and DST — and a small set of rules that prevent the most common date-handling bugs.

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