UTC

basis for uniform calculation of time in all parts of the world that is based on the atomic clock (method that is more modern and precise than GMT)

Coordinated Universal Time (UTC) is a high-precision atomic time standard. UTC has uniform seconds defined by International Atomic Time (TAI), with leap seconds announced at irregular intervals to compensate for the earth's slowing rotation and other discrepancies. Leap seconds allow UTC to closely track Universal Time (UT), a time standard based not on the uniform passage of seconds, but on the Earth's angular rotation.
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Noun
1. Greenwich Mean Time updated with leap seconds
(synonym) coordinated universal time
(hypernym) Greenwich Mean Time, Greenwich Time, GMT, universal time, UT, UT1
(hyponym) Earth-received time, ERT

Abbreviation for Coordinated Universal Time.

Time scale, based on the second (SI), as defined and recommended by the CCIR, and maintained by the Bureau International des Poids et Mesures (BIPM). For most practical purposes associated with the Radio Regulations, UTC is equivalent to mean solar time at the prime meridian (0° longitude), formerly expressed in GMT. [NTIA] [RR] Note 1: The maintenance by BIPM includes cooperation among various national laboratories around the world. Note 2: The full definition of UTC is contained in CCIR Recommendation 460-4. (188 ) Note 3 : The second was formerly defined in terms of astronomical phenomena. When this practice was abandoned in order to take advantage of atomic resonance phenomena ("atomic time") to define the second more precisely, it became necessary to make occasional adjustments in the "atomic" time scale to coordinate it with the workaday mean solar time scale, UT-1, which is based on the somewhat irregular rotation of the Earth. Rotational irregularities usually result in a net decrease in the Earth's average rotational velocity, and ensuing lags of UT-1 with respect to UTC. Note 4: Adjustments to the atomic, i.e., UTC, time scale consist of an occasional addition or deletion of one full second, which is called a leap second. Twice yearly, during the last minute of the day of June 30 and December 31, Universal Time, adjustments may be made to ensure that the accumulated difference between UTC and UT-1 will not exceed 0.9 s before the next scheduled adjustment. Historically, adjustments, when necessary, have usually consisted of adding an extra second to the UTC time scale in order to allow the rotation of the Earth to "catch up." Therefore, the last minute of the UTC time scale, on the day when an adjustment is made, will have 59 or 61 seconds. Synonyms World Time, Z Time, Zulu Time.

Coordinated Universal Time (UTC), as kept by the "i" laboratory, where i is any laboratory cooperating in the determination of UTC. Note: In the United States, the official UTC is kept by the U.S. Naval Observatory and is referred to as UTC (USNO).

Coordinated Universal Time