I have two supposedly identical Linux builds based on
# uname -a
Linux localhost.localdomain 2.6.20-1.2320.fc5 #1 Tue Jun 12 18:50:38 EDT 2007 i686 i686 i386 GNU/Linux
They both have their ntp servers synched to Greenwich time and in the ntp tab of the Date and Time admin menu has the "uses UTC Time". They are synched (as are all the computers in our local domain) to an atomic-clock derived ntp server.
But one says:
Mon Dec 29 20:47:27 UTC 2008
and the other says:
Mon Dec 29 20:47:27 GMT 2008
I wouldn't be concerned about this, but when I synchronize files between the two systems, I end up with clock skew problems when building on the GMT box until I touch every file that has been changed recently.