Coordinated Universal Time
Coordinated Universal Time or UTC, also sometimes referred to as "Zulu time", the basis for civil time, differs by an integral number of seconds from atomic time and a fractional number of seconds from UT1. Time zones around the world are expressed as positive and negative offsets from UTC. UTC is the successor of Greenwich Mean Time, abbreviated as GMT, and is still colloquially called GMT sometimes. The new name was coined to eliminate having the name of a specific location in an international standard. UTC bases time measurement on atomic standards rather than GMT's celestial ones.