Time difference calculator

The default zones in winter and summer

How to use it

1. Edit any of the three zone boxes. Each takes an IANA name like America/Chicago or Europe/Paris.
2. The card for that zone updates with its current local time as you type a valid name.
3. Compare the cards to read the difference in hours and minutes between the zones.
4. If a card shows n/a, the name is not recognized. Check the spelling, capital letters, and the underscore in names like New_York.

Why the gap between two cities changes

The difference between two zones is constant only when neither observes daylight saving time, or both switch on the same dates. The United States moves its clocks on the second Sunday in March and the first Sunday in November. The European Union switches on the last Sundays of March and October. For a few weeks each year New York and London are four hours apart instead of five.

Zones that never change, such as Asia/Tokyo, shift relative to both when the others switch.

Finding zone names

IANA names use a region and a city: America/Chicago, Europe/Berlin, Australia/Sydney. The city is the zone's representative, not the only place in it. Denver, Salt Lake City, and Albuquerque all use America/Denver. If you do not know the name, click the place in the time zone finder and copy it from the result.

How the times are computed

The browser's Intl API formats the current moment in each zone using the time zone database built into your browser. No server is asked, so the cards work offline. Browsers update that database with their own releases, so a zone whose rules changed very recently can lag until your browser updates.

Scheduling across zones

For a call across three zones, find the hours when all three cards show daytime. Between the US East Coast and Western Europe, mornings in New York overlap with afternoons in London. Between the US and East Asia, evenings in the US overlap with the next morning there.

Recheck times in March, October, and November, when daylight saving changes shift the gaps. Arizona and Hawaii do not observe daylight saving time, so their gap to other US zones changes by an hour twice a year.