Coordinated Universal Time
Coordinated Universal Time (UTC,[1] Fr. Temps Universel Coordonné) is a time standard based on International Atomic Time (TAI) with leap seconds added at irregular intervals to compensate for the Earth’s slowing rotation.[2] Leap seconds are used to allow UTC to closely track UT1, which is mean solar time at the Royal Observatory, Greenwich. The difference between UTC and UT1 cannot exceed 0.9 seconds, so if high precision is not required the general term Universal Time (UT) (without a suffix) may be used. In casual use, Greenwich Mean Time (GMT) is used to mean either UTC or UT1. Owing to the ambiguity as to whether UTC or UT1 is meant, GMT is generally avoided in technical contexts. Time zones around the world can be expressed as positive or negative offsets from UTC; UTC replaced GMT as the basis for the main reference time scale or civil time in various regions on January 1, 1972.[3] Coordinated Universal Time is abbreviated UTC.
