영국 그리니치 천문대를 지나는 본초 자오선을 기준으로 설정한 세계 표준시.
The mean solar time at the Royal Observatory in Greenwich, London, formerly used as the international standard for timekeeping.
예문:
"The international flight will depart at 08:00 GMT."
"In the winter, London follows GMT, but it switches to British Summer Time in March."
"Korea Standard Time is exactly nine hours ahead of GMT."