Universal Time

<time, standard> (UT) The mean solar time along the prime meridian (0 longitude) that runs through the Greenwich Observatory outside of London, UK, where the current system originated.

UT is tied to the rotation of the Earth in respect to the fictitious "mean Sun".

Greenwich Mean Time (GMT) was measured from Greenwich mean midday until 1925 when the reference point was changed from noon to midnight and the name changed to "Universal Time".

There are three separate definitions, UT0, UT1, and UT2, depending on which corrections have been applied to the Earth's motion.

Coordinated Universal Time is kept within 0.9 seconds of UT1, by addition of leap seconds to International Atomic Time.

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universal quantifier Universal Resource Identifier Universal Resource Locator Universal Serial Bus universal thunk	Coordinated Universal Time CUT GMT Greenwich Mean Time International Atomic Time	Universal Time Coordinated University of Arizona University of California at Berkeley University of Durham University of East London