A leap second added on New Year's Day

A leap second will be added to the Coordinated Universal Time (UTC) at 7:59:59am on January 1 (New Year's Day), Hong Kong time. The Hong Kong standard time, which is exactly eight hours ahead of UTC, will be delayed by one second accordingly. The whole process will be completed in 2 seconds, at 8:00:00am Hong Kong time.

UTC is a stable and even time scale based on the frequency of atomic oscillations in atomic clocks. This is the current international time scale for civil use.

The astronomical time scale based on the Earth's rotation is another common time scale. As a result of atmospheric circulation and other geophysical events on Earth, the rate of the Earth's rotation is uneven and slowing down. At present, one second based on the astronomical time scale is slightly longer than that on the standard atomic time scale. It is therefore necessary to introduce a leap second from time to time to reconcile the two time scales so that the difference between the two time scales is kept to less than 0.9 of a second.

Leap seconds have been introduced 24 times since the adoption of UTC in 1972. The last adjustment was made on January 1, 2006.

More information on leap seconds can be found at:

http://www.weather.gov.hk/en/gts/time/basicterms-leapsecond.htm