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A Leap Second Will Be Added December 31, 2016

Because Earth is slowing down, we will synchronize our clocks by adding a leap second just before we enter 2017.

In Washington DC, the previous leap second occurred on Saturday, December 31, 2016 at 6:59:60 pm.
UTC time was December 31, 2016 at 23:59:60.

Stop Watch clock at midnight multi colored lights in the background

Wait a second before welcoming 2017.


Just before midnight on New Year's Eve 2016 UTC time, a leap second will be added to Coordinated Universal Time (UTC), which is the world's main time standard.

Earth Is Slowing Down

Leap seconds are added either at the end of June or December approximately every 18 months in order to synchronize clocks worldwide with the Earth's slowing rotation.

Every 6 months, the International Earth Rotation and Reference Systems Service (IERS) in Paris, France announces whether a leap second needs to be added based on how much Earth's rotation speed has changed.

Added to UTC and Local Times

Leap seconds are added to UTC, which means that only areas which follow UTC/GMT will have the leap second added to their last minute of 2016. These areas are: The United Kingdom, Ireland, Iceland, Portugal, Morocco, and Ghana.

All other time zones are offset from UTC, and will have the leap second added at the corresponding local time.

Did You Notice?

The previous leap second was added on June 30, 2015 at 23:59:60 UTC. The difference between UTC and International Atomic Time (UTC-TAI) is now 36 seconds.

Up for Debate

Removing leap seconds has been proposed on several occasions, and would mean a major change of our global timekeeping system.