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Old 8th Feb 2009, 12:34
  #43 (permalink)  
iws
 
Join Date: Feb 2006
Location: Nr. Edinburgh
Posts: 18
It all depends on what you mean by what the time is.

If you are thinking of clock time, that is locked to the Earth's rotation, so that the Sun rises at the correct times every year, and transits of stars measured by telescopes are still used for calibration.

Unfortunately, the Earth is slowing down due to tidal friction from the Moon and Sun, so Earth time has to be adjusted every so often to keep it in sync with the more accurate Atomic (Cesium) time. This is done by inserting "Leap Seconds" into the Earth (UTC or GMT) time.
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