Believe it or not, there is more than one time.
See
http://tycho.usno.navy.mil/systime.html for some well(?) known ones.
To make it even more interesting, there can be differences between them.
This is mainly due to 'leap seconds' - basically a tweak every 6 months or so, to help syncronise times between the systems.
So as of 1 January 1999,
International Atomic Clock is ahead of UTC by 32 seconds.
GPS is ahead of UTC by 13 seconds.
At least thats my argument when Mrs Seat Of My Pants says "You promised to be home at 10:30" - Ah but which time system?