UTC is the abbreviation of Coordinated Universal Time
Coordinated Universal Time（French: Temps Universel Coordonné）is the most important world time standard, which is based on atomic time seconds and is as close to Greenwich mean time as possible. The people's Republic of China adopts the national standard GB / T of ISO 8601:2000. Coordinated universal time (UTC) is the main time standard in the world to adjust the clock and time. The difference between UTC and the flat solar time of 0 degree longitude is not more than 1 second, and it does not comply with the daylight saving time. Coordinated universal time is one of several alternative time systems closest to Greenwich mean time (GMT). For most applications, UTC time is considered to be interchangeable with GMT time, but GMT time is no longer determined by the scientific community. UTC is based on International Atomic Time (IAT) and offsets the slowing down of the earth's rotation by adding leap seconds irregularly. Leap seconds are inserted into UTC when necessary to ensure that the difference between coordinated universal time (UTC) and universal time (UT1) is not more than 0.9 seconds.