greenwich_time has definitions from the field of geography
1
[ noun ] (geography) the local time at the 0 meridian passing through Greenwich, England; it is the same everywhere

Used in print

(L. Don Leet and Florence J. Leet, editors, The World of...)

At 17_:_07 that afternoon ( Greenwich_time ) the shock was recorded by the seismograph alarm in Honolulu .

While accounts of the progress of the tsunami came_in from various points in the Pacific ( Midway reported it was covered with nine feet of water ) , the Hawaiian station made its calculations and notified the military_services and the police that the first big wave would arrive_at Honolulu at 23_:_30 Greenwich_time .

*