In a few weeks, most Americans will have to switch their clocks back one hour as daylight saving time ends and switches to ...

Daylight saving time became a national standard in 1966 when President Lyndon B. Johnson signed the Uniform Time Act, which ...

How do we know the time... precisely? The question is more complex than it first appears, says Richard Fisher.

How do we know the time... precisely? The question is more complex than it first appears, says Richard Fisher.

Atomic scientists reset the Doomsday Clock on Tuesday, moving its hands to 90 seconds to midnight - closer than ever before to the threat of annihilation.

Satellite navigation systems for lunar settlements will require local atomic clocks. Researchers are figuring out what time they will keep.

Even guardians of America's atomic clocks say time doesn't work the way we think it does.

Investigations of the simplest possible clocks have revealed their fundamental limitations — as well as insights into the nature of time itself.