Conversion of GMT/UTC to Local Time

The date and time of earthquake occurrence is expressed in either local time [e.g., Mountain Standard Time (MST), Mountain Daylight Time (MDT)] or in Greenwich Mean Time (GMT). GMT time (sometimes referred to as Coordinated Universal Time or UTC) is the time along the prime meridian through Greenwich, England, and is used as a time standard throughout the world. Local time (MST) is 7 hours behind GMT (i.e., local time = GMT – 7 hours). [During three time periods, GMT was 6 hours earlier than MST (02:00 Mar. 30, 1918 to 02:00 Oct. 27, 1918; 02:00 Mar. 30, 1919 to 02:00 Oct. 26, 1919; and 02:00 Feb. 9, 1942 to 02:00 Sept. 30, 1945)]. Seismologists routinely convert from local time to GMT for research purposes to avoid potential problems in translating between time zones around the world.