Greenwich time
Zero meridian hour
Greenwich time is the local time at the Royal Observatory in Greenwich, England, historically used as the reference point for global timekeeping.
Before standardized time zones, clocks worldwide were set relative to Greenwich: The ship's chronometer was synchronized to Greenwich time.
Now largely replaced by the term Coordinated Universal Time (UTC), though the two are nearly identical.
- GMTGlobal time baseline
- UTCUniversal time standard
- meridianPole-to-pole great circle
- longitudeEast-west angular distance
- observatoryFacility for celestial study
prime · Royal Observatory · London · clock · standard · timezone · prime meridian · naval · chronometer · coordination · international · dateline · noon · sundial · astronomy · navigation · England · seconds
- celestial navigationcelestial navigation, sextant, astrolabe, nautical almanac, celestial sphere
- ship timewatch, first watch, morning watch, dog watch, midwatch