'Leap second' adds extra moment for first time since 2008
File photo of a time change. (Moscow-Pullman Daily News, Geoff Crimmins)
Published Friday, June 29, 2012 11:01AM EDT
Last Updated Friday, June 29, 2012 10:44PM EDT
The Canada Day long weekend just got a little longer – only by one second unfortunately.
Saturday will be one second longer this year as a team at the Paris Observatory adds a “leap second” just before midnight to compensate for a gradual slowdown in the Earth’s rotation.
International Earth Rotation and Reference System Service experts make the adjustment when the planet’s movement falls out of sync with atomic clocks used to measure time.
A total of 24 seconds have been added to atomic clocks since 1972.
But that doesn’t mean that days are 24 seconds longer, only that the days on which the leap second are added have 86,401 instead of the usual 86,400 seconds.
A second can be added or removed as needed every six months, but it typically happens only every 1.5 years.
Saturday’s change comes after nearly four years without a leap second - the last one was at the end of December 2008.
Atomic clocks only deviate one second every 20 million years or so, but the Earth’s rotation isn’t that reliable, so the time adjustment is necessary.