It would take 15 billion years for the clock that occupies Jun Ye's basement lab at the University of Colorado to lose a second—about how long the universe has existed. For this invention, the Chinese ...

Einstein's theory of general relativity holds that a massive body like Earth curves space-time, causing time to slow as you approach the object—so a person on top of a mountain ages a tiny bit faster ...

Time zones are a complicated but necessary evil. Humans like the numbers on the clock to vaguely match up with what the sun is doing in the sky outside. To that end, different places in the world keep ...

Custodian Ray Keen inspects a clock face. A new study says world clocks will need a "negative leap second" to stay accurate. (Charlie Riedel/AP) ...