World Clock — Current Time in Any Timezone
Track the current time across multiple timezones at once, with daylight saving handled from the IANA timezone database.
Why timezone names beat offsets
A timezone is not an offset. An offset is what a zone happens to be at one instant; the zone is the set of rules that determines the offset at every instant, past and future.
"UTC+1" tells you nothing about next January. "Europe/London" tells you it will be UTC+0 then and UTC+1 in summer, and it encodes when those transitions happen — including the fact that the UK observed British Double Summer Time during the Second World War, and that the transition dates changed in 1972 and again in 1981.
That history lives in the IANA timezone database (also called tz or zoneinfo), which every operating system and language runtime ships. It is updated several times a year, because governments change these rules with little notice — and sometimes with weeks of notice, which is why an out-of-date tzdata is a real source of production bugs.
Zone names look like Area/Location: Europe/London, America/New_York, Asia/Kolkata. The location is a representative city, not a country, because countries can span several zones and can change which zone a region belongs to. Abbreviations like IST are useless in software — IST is Indian Standard Time, Irish Standard Time and Israel Standard Time simultaneously.
Timezone facts that break naive assumptions
| Assumption | Reality |
|---|---|
| Offsets are whole hours | India is UTC+5:30, Nepal UTC+5:45, parts of Australia UTC+8:45 |
| Offsets range ±12 | Kiribati is UTC+14 — 26 hours ahead of Baker Island at UTC−12 |
| DST always means +1 hour | Lord Howe Island shifts by 30 minutes |
| DST happens in the northern summer | Southern hemisphere zones shift in the opposite half of the year |
| Every country observes DST | Most of Asia and Africa do not; several countries have abolished it recently |
| A country has one timezone | The US has six; China has one despite spanning five geographic zones |
| DST transitions happen at 2am | Varies — Brazil used midnight, and Lord Howe uses 2am local which is a different UTC instant |
| A date always exists | 30 April 2026 does not exist in Kiribati’s Line Islands, which skipped a day in 1995 to change side of the date line |
Scheduling across zones without getting it wrong
- Store the zone, not the offset —A meeting stored as "+01:00" will be an hour wrong after the next DST transition. Stored as "Europe/London" it stays correct.
- For future events, store local time plus zone —A 9am standup should stay at 9am even if the government changes the DST rules. Storing it as a UTC instant means it silently moves to 8am or 10am.
- For past events, store the UTC instant —What happened, happened. A log entry or an audit record should be a fixed instant that no rule change can alter.
- Avoid scheduling between 00:30 and 03:30 local —That window contains every DST transition. Anything scheduled there will one day run twice or not at all.
- Keep tzdata current —Governments announce changes with as little as a few weeks’ notice. A container image pinned two years ago has stale rules, and the failure is silent.
About
The World Clock displays your local time on a live analog clock face and lets you add clocks for major cities around the world. It is useful for scheduling calls across time zones, tracking team members in different countries, or just checking the current time anywhere on the globe.
How to use
- 1 Your local clock is displayed automatically when the page loads.
- 2 Click Add City to add a world clock for any major city.
- 3 Remove a city clock by clicking the × icon.
- How does the world clock know my local time?
- The clock reads your local time directly from your device using the browser's Date API. No location permission is required, and your location is never sent to any server — the time is determined entirely from your device's system clock and timezone settings.
- Does the world clock handle daylight saving time automatically?
- Yes. All city clocks use the IANA timezone database (the same one used by operating systems and browsers) which automatically applies the correct daylight saving time offsets for each city throughout the year.
- How many cities can I add to the world clock?
- You can add as many city clocks as you need. The clocks are displayed in a responsive grid, so adding more cities simply expands the grid. Your selections are saved in browser local storage so they persist between visits.
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