Coordinated Universal Time - UTC replaced Greenwich Mean Time on 1 January 1972 as the basis for the main reference time scale or civil time in various regions. Time zones around the world are expressed as positive or negative offsets from UTC. Local time is UTC plus the time zone offset for that location, plus an offset (typically +1) for daylight saving time, if in effect. UTC is also referred to by the military and civil aviation as Zulu time (Z).
