UTC — Coordinated Universal Time

Coordinated Universal Time (UTC) is the primary time standard by which the world regulates clocks and time. It is the successor to Greenwich Mean Time (GMT) as the international civil time standard and was officially adopted in 1972. UTC is maintained by a network of atomic clocks around the world, coordinated by the International Bureau of Weights and Measures (BIPM) in Paris, and is accurate to within a nanosecond per day.

The abbreviation UTC is a compromise between the English "Coordinated Universal Time" and the French "Temps Universel Coordonne" (TUC), with neither language's acronym taking precedence. UTC differs from the older GMT standard in that it is based on International Atomic Time (TAI) with leap seconds added at irregular intervals to keep it within 0.9 seconds of mean solar time at the prime meridian. These leap seconds account for the gradual slowing of Earth's rotation.

UTC is not a time zone in the traditional sense but rather a time standard from which all time zones are defined as offsets. It is used directly by aviation (where it is called "Zulu time"), maritime navigation, the International Space Station, and many internet protocols and computing systems. No country uses UTC as its official civil time, though Iceland and several West African nations use UTC+0, which is functionally identical.