Definitions for

**"Universal Time"****Related Terms:**Gmt, Universal coordinated time, Greenwich mean time, Utc, Coordinated universal time, Standard time, Local time, Time zone, Lst, Tdt, Mean time, Tai, Equation of time, Solar noon, Daylight saving time, Epoch, Elapsed time, Travel time, Mdt, Solar time, Sidereal time, Pst, Leap second, Eta, Ephemeris time, Start time, Solar day, Ete, Time of flight, Day, Absolute time, Sidereal day, Analemma, Mean solar time, Mean sun, Moment, Lunar day, Lag , International date line, Split time, Time, Hour angle, Nautical almanac, Period, Lag time, Time scale, Sidereal month, Pause , Sidereal year

Universal time is approximately the same as Greenwich Mean Time (GMT). Like GMT UT does not include daylight saving changes. The US Naval Observatory has more information about universal time.

Greenwich Mean Time (GMT). Time referred to the zero meridian of longitude (through Greenwich, UK). 0000 UT is local midnight at Greenwich. For example, 00 UT = 10 am Australian EST = 8 am Australian WST = 9.30 am Australian CST.

Standard time at the Prime Meridian passing through Greenwich, England. Also called Coordinated Universal Time, because it is an average of the time kept by atomic clocks in various countries.

a measure of time that conforms, within a close approximation, to the mean diurnal motion of the Sun and serves as the basis of all civil timekeeping. UT is formally defined by a mathematical formula as a function of sidereal time. Thus UT is determined from observations of the diurnal motions of the stars. The time scale determined directly from such observations is designated UT0: it is slightly dependent on the place of observation. When UT0 is corrected for the shift in longitude (see longitude, terrestrial) of the observing station caused by polar motion, the time scale UT1 is obtained.

The system time, equivalent to GMT. See also: home time

the local time at the 0 meridian passing through Greenwich, England; it is the same everywhere

See Coordinated Universal Time.

UT) local time on the Greenwich meridian

See GMT.

Mean solar time on the Prime Meridian. Also called Greenwich Mean Time.

A measure of time used by astronomers; UT conforms (within a close approximation) to the mean daily (apparent) motion of the sun. UT is determined from observations of the diurnal (daily) motions of the stars for an observer on the earth. UT is usually used for astronomical observations, while Terrestrial Dynamical Time (TDT, or simply TT) is used in orbital and ephemeris computations that involve geocentric computations. Coordinated Universal Time (UTC) is that used for broadcast time signals (available via shortwave radio, for example), and it is within a second of UT.

The time at the longitude of Greenwich, England. Universal Time is widely used in international publications as a standard time.

(UT) refers to Coordinated Universal Time (UTC) which is the basis for worldwide civil time. It is determined from use of highly precise atomic clocks.

A measure of time that relates closely to the Sun's daily apparent motion and serves as the basis for civil timekeeping. It is formally defined by a mathematical formula that links it to sidereal time, and is thus determined from observations of the stars.

Similar to Greenwich Mean Time

the local time of day on a line of longitude centered on Greenwich, England (also known as Greenwich Mean Time); it forms the basis for all civil timekeeping

Also known as Greenwich Mean Time, this is local time on the Greenwich meridian. Universal time is used by astronomers as a standard measure of time.

Abbreviated UT. The same as Greenwich Mean Time (GMT) in England. US Eastern Standard Time (EST) is five hours earlier than Universal Time.

Local solar mean time at Greenwich Meridian. Some commonly used version of Universal Time are

The standard clock for astronomical purposes, synonymous for all practical purposes with Greenwich Mean Time (GMT). Many astronomical events are listed in UT, from which an adjustment must be made for local time. For example, Mountain Standard Time is 7 hours earlier than UT, Mountain Daylight Time 6 hours earlier. Therefore 1h UT on Nov. 13 = 1800 (6 p.m.) MST on November 12.

(UT) - Same a Greenwich mean time (GMT).

The international standard time reference that was formerly called Greenwich Mean Time. It is also called universal coordinated time or UCT.

(Abbreviated UT.) The basis for civil timekeeping. It is formally defined by a mathematical formula which relates UT to Greenwich mean sidereal time. Depending on the context, universal time and UT are commonly used to mean 1) UT0, which is dependent on the observer's location; 2) UT1, which removes the effect of the motion of the geographic pole; or 3) coordinated universal time (UTC). Since 1 January 1972, weather services have used UTC as the standard of time. See also zone time United States Naval Observatory and her Majesty's Nautical Almanac Office, Annual: The Astronomical Almanac, U.S. Government Printing Office, Washington, D.C. and HMSO, London, England.

The system time, equivalent to GMT. See also: local time

A high precision atomic clock time standard that replaces the historic Greenwich Mean Time. It is 7 hours ahead of VENUS local time during Pacific Daylight Saving Time (PDT), and 8 hours ahead during periods of Pacific Standard Time (PST), so you must subtract 7 hours from UTC and 8 hours from UTC, respectively, to get local time for VENUS during those periods. See the corresponding Wikipedia article for more detail.

The local mean time of the prime meridian. It is the same as Greenwich mean time, counted from 0 hour beginning at Greenwich mean midnight.

Abbreviated UT. A time system used internationally for recording the timing of events, particularly in astronomy. The same as Greenwich Mean Time (GMT).

( UT) The mean solar time of the meridian at the Prime Meridian. Universal Time replaced the time standard known as Greenwich Mean Time in 1928. Universal Time is commonly used to denote solar time.

time, represented as a non-negative integer number of seconds. Absolute universal time is measured as an offset from the beginning of the year 1900 (ignoring leap seconds). See Section 25.1.4.2 Universal Time.

Universal Time (UT) is a timescale based on the rotation of the Earth. It is a modern continuation of the Greenwich Mean Time (GMT), i.e., the mean solar time on the meridian of Greenwich, England, which is the conventional 0-meridian for geographic longitude. GMT is sometimes used, incorrectly, as a synonym for UTC.