GMT

time at Greenwich (England) used as the basis for calculating time zones around the world (also g.m.t.)

Greenwich Mean Time (GMT) is a term originally referring to mean solar time at the Royal Observatory, Greenwich in England. It is now often used to refer to Coordinated Universal Time (UTC) when this is viewed as a time zone, although strictly UTC is an atomic time scale which only approximates GMT in the old sense. It is also used to refer to Universal Time (UT), which is the astronomical concept that directly replaced the original GMT.
See more at Wikipedia.org...

Noun
1. the local time at the 0 meridian passing through Greenwich, England; it is the same everywhere
(synonym) Greenwich Mean Time, Greenwich Time, universal time, UT, UT1
(hypernym) time
(hyponym) coordinated universal time, UTC

GMT, greenwich mean time; time at Greenwich

Greenwich Mean Time, time at Greenwich (London) used as the basis for calculating standard times around the world