Atomic Clock: Exact Time with Seconds
How this clock stays accurate
This page shows the exact time with seconds in Coordinated Universal Time (UTC), the reference that every time zone in the world is defined against. UTC is kept by a worldwide network of atomic clocks, which measure the length of a second far more precisely than any quartz or mechanical clock.
The clock above starts from the time on our server and then keeps counting in your browser, checking back with the server every hour. That way it stays accurate to the second even if your own device's clock has drifted, which is common: an ordinary quartz clock can gain or lose up to 15 seconds a month, while the atomic clocks behind UTC stay within a second over 100 million years.
Looking for a different place? Open the time zone map, browse all time zones, or find the time by country. To measure time rather than read it, use our timer or stopwatch. For the calendar side of the same UTC reference, see what week it is.