(koto_feja/Getty Images) A breakthrough in chronometry decades in the making could redefine the limits of how we keep time.

A clock built from thorium-229 has crossed an important line, from a long-discussed concept to a working device. The shift ...

Resembling a squat, wide fridge, the world's most accurate clock went on sale for $3.3 million in Japan on Wednesday. The "Aether clock OC 020" is so precise that it would take 10 billion years for it ...

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) ...