World Clock
World Clock — runs in your browser. Inputs are not stored.
World clock
Enter values, then press Calculate.
Shows major cities in their Intl time zones. Display may vary with the browser’s locale and time-zone support.
How to use
- When you open the page, the city list is drawn immediately and the time updates every second. There is no separate start button.
- Each row shows the city name, IANA time zone, and year, month, day, weekday, hour, minute, and second in 24-hour time.
- If the display looks frozen, press Refresh now to redraw immediately. It is the same list as the automatic update.
- Cities are fixed: Seoul, Tokyo, Beijing, Singapore, Dubai, Moscow, London, Paris, New York, Los Angeles, and Sydney.
- There is no custom city, favorites, or analog hands. If you only need a large local clock, use the online clock.
- On older browsers that do not know a time zone, that row may show an unsupported time zone.
Key concepts
A world clock shows the same instant in several time zones. This screen passes each city’s timeZone into Intl.DateTimeFormat and formats in the Korean locale, 24-hour. If the device clock is wrong, every city is wrong together.
London, Paris, New York, Los Angeles, and Sydney with daylight saving follow the rules the browser knows. You do not enter an offset yourself. To turn UNIX seconds into a number, use the timestamp converter. There is no field to search city names or reorder the list. If your travel city is missing, check that region’s standard time separately. Display uses the Korean locale.
Example
When Seoul is Tuesday 3 p.m., the New York row immediately shows whether it is the previous day’s early morning or the same day’s morning. Before an overseas video call, open this list, check London, New York, and Sydney side by side, then use Refresh now to align seconds if needed. When Seoul is Monday 9 a.m., you can see at a glance whether the London row is near Sunday midnight, so leave the list open when choosing an email send time.
Related: Online clock · Timestamp converter · Countdown timer
Frequently asked questions
Can I add my city to the world clock?
No. Only eleven major cities from Seoul to Sydney are fixed. For a large device-local clock, use the online clock.
Is the world clock server time or my computer time?
It converts the device time into each time zone. It does not sync with a network time server.
Is daylight saving automatic on the world clock?
It follows the browser’s Intl time-zone rules. There is no separate DST switch.
The world clock shows an unsupported time zone.
That is shown when the time-zone string is missing in the browser. Open it again in a current browser.
Do I have to press Refresh now on the world clock?
Usually it updates every second automatically. Press Refresh now only if the screen looks frozen.
Does the world clock also show UNIX timestamps?
No. For numeric timestamp conversion, use the timestamp converter.
Last reviewed: 2026-09-04