| the time as measured on the prime meridian running through Greenwich, England: used in England and as a standard of calculation elsewhere. |
Green·wich Mean Time  (grěn'ĭch, grĭn'ĭj)  n. Abbr. GMT See universal time. |
| universal time n. Abbr. UT The mean solar time for the meridian at Greenwich, England, used as a basis for calculating time throughout most of the world. Also called Greenwich time, Greenwich Mean Time, Zulu time. |
| Greenwich Mean Time (grěn'ĭch) Pronunciation Key
See universal time. |
Greenwich Mean Time 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)