Greenwich Time

noun
1.
the time as measured on the prime meridian running through Greenwich, England: used in England and as a standard of calculation elsewhere.
Also called Greenwich Mean Time, Greenwich Civil Time, universal time, Universal Time.
Origin
1840-50
British Dictionary definitions for greenwich mean time

Greenwich Mean Time

noun
1.
mean solar time on the 0° meridian passing through Greenwich, England, measured from midnight: formerly a standard time in Britain and a basis for calculating times throughout most of the world, it has been replaced by an atomic timescale GMT See universal time
Usage note
The name Greenwich mean time is ambiguous, having been measured from mean midday in astronomy up to 1925, and is not used for scientific purposes. It is generally and incorrectly used in the sense of universal coordinated time, an atomic timescale available since 1972 from broadcast signals, in addition to the earliest sense of universal time, adopted internationally in 1928 as the name for GMT measured from midnight
greenwich mean time in Science
Greenwich Mean Time
  (grěn'ĭch)   
See universal time.
greenwich mean time in Technology
time, standard
(GMT) The local time on the Greenwich meridian, based on the hypothetical mean sun (which averages out the effects of the Earth's elliptical orbit and its tilted axis). GMT is the basis of the civil time for the UK.
In 1925 the reference point was changed from noon to midnight and it was recommended that the term "Universal Time" should be used for the new GMT.
Authorities disagreed on whether GMT equates with UT0 or UT1, however the differences between the two are of the order of thousandths of a second. GMT is no longer used for scientific purposes.
(2001-08-02)