replaced GMT as the world reference for time. UTC is based on atomic clock time, with leap seconds added when necessary to match earth-motion time. Many data sets collected around the world are recorded with a UTC time stamp to avoid the confusion associated with time zones and daylight saving time. For more information, straight from the United States' official timekeepers, see the National Institute of Standards and Technology (NIST) World Time Scales. For the correct UTC time, see NIST's Official U.S. Time.
(UTC) - a global time scale based on the local time observed on the Prime Meridian; also called Greenwich Mean Time (GMT) or Zulu (Z) time
The 24 hour time system on Earth in which the Prime Meridian is the 0 hour and all other time zones are computed plus (to the east of the Prime Meridian) or minus (to the west of the Prime Meridian) from this time based on the individual zone's location. Also called "Greenwich Mean Time" or "Zulu Time". Astronomical times are given in Universal Coordinated Abbr. UTC, UT.