Coordinated Universal Time is the primary time standard by which the world regulates clocks and time.
It is within about 1 second of mean solar time at 0° longitude, and does not observe daylight saving time.
For most purposes, UTC is considered interchangeable with Greenwich Mean Time, but GMT is no longer precisely defined by the scientific community.
This abbreviation arose from a desire by the International Telecommunication Union and the International Astronomical Union to use the same abbreviation in all languages. English speakers originally proposed CUT (for "coordinated universal time"), while French speakers proposed TUC (for "temps universel coordonné"). The compromise that emerged was UTC which conforms to the pattern for the abbreviations of the variants of Universal Time (UT0, UT1, UT2, UT1R, etc).