World Clock

How time zones work

A time zone is a region of the world that keeps the same official time. Every zone is defined as an offset from Coordinated Universal Time (UTC), the global reference kept by atomic clocks. When it is 12:00 UTC, a city at UTC−5 reads 07:00 and a city at UTC+9 reads 21:00. The clocks on this page are all measured against UTC, so they stay in step with each other to the second.

Offsets run from UTC−12 in the far west Pacific to UTC+14 in the Line Islands of Kiribati: a 26-hour spread, which is why two places can be on different calendar dates at the same instant. Most offsets are whole hours, but a few regions sit on the half-hour (India at UTC+5:30) or even the quarter-hour (Nepal at UTC+5:45). The International Date Line, roughly along the 180° meridian, is where each new day begins.

Many countries also shift their clocks for daylight saving time (DST), moving forward an hour in spring and back in autumn. Because not every region observes DST, and those that do change on different dates, the gap between two cities isn't fixed: London and New York are usually 5 hours apart, but for a couple of weeks each year they're 4. Every clock here is DST-aware and recalculates automatically, so a conversion is correct whatever the season.

To find a place quickly, use the search box above, click a continent on the map, or open a region below. Each city has its own page with a live clock, current UTC offset, upcoming daylight-saving change, sunrise and sunset, and time differences to other cities, and the time zone converter and meeting planner turn any of them into a side-by-side comparison.