Reconciliation of the observed differences between an ensemble ofДЄtomic clocks maintained by a number of national time bureaus. Highest precision after the fact, as atomic time is determined by the International standard UTC time can only be determined to the The IERS announced in July 2005 that the next leap secondДЇor most practical and legal-trade purposes, the fractionalДifference between UTC and UT (or, GMT) is inconsequentially small, andДЇor this reason UTC is colloquially called GMT sometimes, even if this The deceleration of the Earth's rotation slowed temporarily in the past However a leap second has not been required since 1998, as Historically, one leap second has been required every one to (IERS), based on precise astronomical forecasts of the Earth's TheДЄnnouncement of leap seconds is made by the International Earth Rotation and Reference Systems Service Where an additive leap second is designated as 23:59:60. have been positive and applied on dates June 30 or December 31, To date, all such adjustments - the first in 1972 Within 0.9В s of UT1 (UT1 is one of three precise definitions of UT) leap secondsДЄre added (or, theoretically, subtracted) at the end of any UTC monthДЄs necessary. For this reason, UT is 'slower' than TAI.

Of the tides), hence the mean solar day has increased since TAI was

The Earth's rotation is very slowly decelerating (due to braking action UTC is a hybrid time scale: the rate of UTC is based on atomic frequency standards but the epoch of UTC is synchronized to remain close to astronomical UT.

UTC differs by an integral number of seconds from International Atomic Time (TAI), as measured by atomic clocks and a fractional number of seconds from UT. Time zones around the world are expressed as positive and negative offsets from UT. UTC also stands for the University of Tennessee at Chattanooga.Д¬oordinated Universal Time or UTC, also sometimes referred to as ' Zulu time', is an atomic realization of Universal Time(UT) or Greenwich Mean Time, the astronomical basis for civil time.

Universal time clock