World Clock
Keep live clocks for the cities that matter to you: search more than 140 cities or any IANA time zone, see who is in daytime or night, and how many hours each place is ahead of or behind you.
Your clocks are saved in this browser. Day and night use the real position of the sun for each city; sunrise and sunset are approximate (± 2 minutes).
How to use the World Clock
- Search for a place: type a city, country or time zone (for example Tokyo, Brazil or Asia/Dubai) and press Enter or click a result.
- Read each card: the local time, date, UTC offset and how far ahead of or behind you it is.
- Check day or night: warm cards are in daylight, purple cards are in twilight and blue cards are at night. Sunrise and sunset are shown below.
- Customise: switch between 24h and 12h, turn on analog dials or sort the clocks by time.
- Remove a city with the × button. Your list is saved automatically for your next visit.
Time differences between major cities
Offsets below are in standard (winter) time for the Northern Hemisphere. Many zones move one hour forward for daylight saving time, so differences can change by an hour for a few weeks in spring and autumn when countries switch on different dates.
| When it is 09:00 in… | New York | London | Dubai | New Delhi | Tokyo |
|---|---|---|---|---|---|
| New York (UTC−05:00) | 09:00 | 14:00 | 18:00 | 19:30 | 23:00 |
| London (UTC+00:00) | 04:00 | 09:00 | 13:00 | 14:30 | 18:00 |
| Dubai (UTC+04:00) | 00:00 | 05:00 | 09:00 | 10:30 | 14:00 |
| New Delhi (UTC+05:30) | 22:30 (prev. day) | 03:30 | 07:30 | 09:00 | 12:30 |
| Tokyo (UTC+09:00) | 19:00 (prev. day) | 00:00 | 04:00 | 05:30 | 09:00 |
How day and night are calculated
For every city the world clock computes the sun's position from the date, the time and the city's coordinates:
- The sun's ecliptic longitude and declination are found from the number of days since 1 January 2000 (the J2000 epoch).
- Sidereal time and the city's longitude give the sun's hour angle, and with the latitude this gives the sun's elevation above the horizon.
- Elevation above −0.833° counts as day (this allows for the sun's radius and atmospheric refraction), −0.833° to −6° is civil twilight, and anything lower is night.
- Sunrise and sunset are the moments when the elevation crosses −0.833°, worked out around local solar noon, which is corrected for the equation of time.
Near the poles the sun may not rise or set at all, and the cards then show polar night or midnight sun.
Unusual time zones worth knowing
- India (UTC+05:30): one time zone for the whole country, half an hour off the hour.
- Nepal (UTC+05:45): one of the few zones with a 45-minute offset.
- China (UTC+08:00): a single zone across the whole country despite its width.
- Kiritimati, Kiribati (UTC+14:00): the first place to start each new day.
- Newfoundland, Canada (UTC−03:30): a half-hour zone in North America.
Frequently asked questions
How does the world clock know the time in each city?
It uses your device's clock together with the time zone database built into your browser (the IANA tz database), which includes daylight saving rules. Each city is linked to its official zone, such as America/New_York or Asia/Kolkata.
Does the world clock handle daylight saving time?
Yes. Offsets change automatically when a country switches to or from daylight saving time, so London shows UTC+01:00 in summer and UTC+00:00 in winter.
How is day and night worked out?
For each city the tool calculates the sun's height above the horizon from its latitude and longitude. Day means the sun is up, twilight means it is less than 6° below the horizon, and night means it is lower than that.
Can I add a place that is not in the city list?
Yes. If you search for a time zone name such as Yerevan or America/Boise, matching IANA time zones from your browser are offered too. For those, day and night are estimated from the local hour.
Why does a card say Tomorrow or Yesterday?
Places far east of you can already be on the next calendar day, and places far west can still be on the previous day. The badge compares each city's date with your own date.
Are my cities saved?
Yes, your list and settings are stored in your browser's local storage on this device only. Nothing is sent to a server.