Source : WordNet®

universal time
     n : the local time at the 0 meridian passing through Greenwich,
         England; it is the same everywhere [syn: {Greenwich Mean
         Time}, {Greenwich Time}, {GMT}, {UT}, {UT1}]

Source : Free On-Line Dictionary of Computing

Universal Time
     
         (UT) The mean solar time along the prime
        meridian (0 longitude) that runs through the Greenwich
        Observatory outside of London, UK, where the current system
        originated.  UT is tied to the rotation of the Earth in
        respect to the fictitious "mean Sun".
     
        {Greenwich Mean Time} (GMT) was measured from Greenwich mean
        midday until 1925 when the reference point was changed from
        noon to midnight and the name changed to "Universal Time".
     
        There are three separate definitions, UT0, UT1, and UT2,
        depending on which corrections have been applied to the
        Earth's motion.  {Coordinated Universal Time} is kept within
        0.9 seconds of UT1, by addition of leap seconds to
        {International Atomic Time}.
     
        (2001-08-02)