2016 Will Be Longer By A ‘Leap Second’

People will be celebrating New Year's Eve a "leap second" longer than usual this 2016.

The International Earth Rotation and Reference Systems Service (IERS) have announced that an extra second will be added on Dec. 31, which means clocks will read 23:59:60 before midnight, the IERS said.

The IERS, the organization that keeps track of time of the world, said that the leap second is needed to ensure Coordinated Universal Time (UCT), which is the official measure of time, is in sync with the changes in the Earth's rotation.

"We can easily change the time of an atomic clock, but it is not possible to alter the Earth's rotational speed to match the atomic clocks," the U.S. Naval Observatory (USNO) representatives said in a press release. The USNO is in charge of the Department of Defense's master clock.

Units of time have since been defined based on the Earth's rotation relative to distant celestial bodies, Space.com reports.

But with the invention of atomic clocks, which maintains precise ticks based on the consistent frequency of microwaves released by certain atoms, experts decided to base the seconds on their natural vibrations.

Atomic seconds and the Earth's rotation do not match, as the spinning of the Earth is affected by the moon's gravitational pull and other factors, which slow down the spinning. The rotation-based time loses to atomic time by 1.5 to 2 milliseconds per day. This means that the two timescales diverge by a full second every 500 to 750 days.

Thus, leap seconds are allowed to make up for the time difference.

The IERS has added 26 leap seconds to atomic clocks since 1972, the most recent of which happened on June 30, 2015. The goal then was to keep the two timescales within 0.9 seconds of each other.