You Didn't Notice - Extra Seconds Added To The Leap Year

You probably didn’t notice, but at 5:00 p.m. in Colorado on New Year’s Eve, an extra second was added to 2016. In fact, a second has been added to the clock 36 other times since 1972.

“Every couple years, we insert a leap second,” explained Andrew Novick. “It’s an extra second and that allows the earth to catch back up to our official time so that the time and the earth stay synchronized.”

Novick is an electrical engineer at the National Institute of Standards and Technology in Boulder. NIST keeps the official time for the United States using atomic clocks based not on a swinging pendulum, but the frequency of cesium atoms.

“The resonance frequency of a cesium atom of a particular state is 9,192,631,770 hertz,” Novick said.

The giant number Novick referenced is really just the standard measurement of one second. It’s used to calibrate super-accurate atomic clocks that are far more stable than the Earth’s rotation.

“Time had been defined by the rotation of the earth, so that’s when leap seconds were developed,” Novick explained.

Atomic clocks were developed in the late 1960s, but the practice of adding leap seconds didn’t start until 1972, Novick said.

NIST keeps in touch with the International Earth Rotation and Reference Systems Service, or IERS, which monitors the Earth’s orientation and rotation. Novick said IERS notifies NIST when a leap second is needed.

“I think it’s important just to keep the earth in step with what time is,” Novick said.

Without leap seconds, the Earth would gradually become more and more out of sync with the official time.
While most will never notice the extra second added to 2016, Novick won’t miss a tic.

“I hope people use (the leap second) for something productive,” Novick said with a laugh.