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A leap second will be introduced to the Coordinated Universal Time (UTC) between 7:59:59am and 8:00:00am (Hong Kong time) on July 1, 2012. The Hong Kong standard time, exactly eight hours ahead of UTC, will be delayed by one second accordingly.
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 based on the standard atomic time scale. It is therefore necessary to add a leap second from time to time to reconcile the two time scales so that the difference between them is kept to below 0.9 of a second.
Leap seconds have been introduced 25 times since the adoption of UTC in 1972. The last adjustment was made on January 1, 2009.
The Observatory advises stakeholders and operators in information technology, telecommunications, transport sectors, etc, to review whether systems under their management can handle leap seconds properly and, if necessary, to consider testing and adjusting their systems to ensure normal operations during and after the introduction of the leap second.
More information on leap seconds can be found at
www.hko.gov.hk/gts/time/basicterms-leapsecond.htm and
www.hko.gov.hk/blog/en/archives/00000119.htm.
Ends/Thursday, April 19, 2012
Issued at HKT 12:00
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