Greenwich Mean Time
Zero meridian hour
Greenwich Mean Time is the time standard based on the solar time at the Royal Observatory in Greenwich, England, located at zero degrees longitude.
Often abbreviated GMT, it serves as a reference point for time zones worldwide—zones are expressed as hours ahead of or behind GMT.
Though largely replaced by Coordinated Universal Time (UTC) for technical purposes, GMT remains common in everyday usage, especially in Britain.
- UTCUniversal time standard
- marine chronometerPrecise nautical timekeeping instrument
- clockDevice displaying time
- GMTGlobal time baseline
- world timeStandardized international timekeeping
standard time · line · nautical charts · atomic clock · prime meridian · Eastern Time Zone · solar time · longitude · Royal Observatory · watch · time signal · noon · celestial navigation · sundial · observatory · prime · England · London
- timekeepingclock, watch, watches, clocks, timer
- time zonesEST, PST, GMT, CST, MST
- GreenwichRoyal Observatory, prime meridian, GMT, Cutty Sark
- chronometersmarine chronometer, balance wheel, mainspring, escapement
- timepiecesclock, wristwatch, pocket watch, stopwatch, wall clock
- ship timewatch, first watch, morning watch, dog watch, midwatch
Greenwich Mean Timedaylight saving time
Seasonal clock advancement practice
British Summer Time · summer time · DST · Pacific Daylight Time · Eastern Daylight Time