Definition: Universal Co-ordinated Time (usually abbreviated UTC) is the name now given to a more accurate version of what used to be known as Greenwich Mean Time and is the time in the timezone that includes the zero meridian where daylight saving time is not in effect. The difference between UTC and GMT is that GMT is tied to the rotation of the Earth directly while UTC is defined via atomic clocks which are kept within one second of GMT by the occasional addition of a leap second.

Also Known As: Greenwich Mean Time, GMT, Zulu Time, z, Temps universel coordonné