The Future of Time: UTC and the Leap Second Earth’s clocks have
always provided Sun time. But will that continue? Before atomic
timekeeping, clocks were set to the skies. But starting in 1972,
radio signals began broadcasting atomic seconds and leap seconds
have occasionally been added to that stream of atomic seconds to
keep the signals synchronized with the actual rotation of Earth.
Such adjustments were considered necessary because Earth’s
rotation is less regular than atomic timekeeping. In January
2012, a United Nations-affiliated organization could permanently
break this link by redefining Coordinated Universal Time. To
understand the importance of this potential change, it’s
important to understand the history of human timekeeping. Go to
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