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Old 8th Feb 2009, 20:10
  #52 (permalink)  
iws
 
Join Date: Feb 2006
Location: Nr. Edinburgh
Posts: 18
As Matt suggested, yes the sky is the final arbiter as regards clock time, because clock time is based on the rotation of the Earth. Essentially clock time requires the Sun to rise and set as close as possible to the same times every year. There are professional Observatories whoes job it is to check the star transits precisely, but any Observatory looking at the stars
can work out the Earth's clock time and compare it with their Atomic clocks, because the measurements of telescope position are so good these days.

If you were in the outback nowadays, you would use GPS. This is locked to Atomic time, but most receivers can read the correction of leap seconds which is broadcast in the GPS signal, and correct to read UTC (Clock time) as necessary.
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