Definition
Mountain Standard Time (MST) is the standard time observed in the Mountain Time Zone of North America, set seven hours behind Coordinated Universal Time (UTC-7). It applies to states such as Arizona, Colorado, Utah, New Mexico, Wyoming, Montana, and parts of Idaho during the standard-time portion of the year. During daylight saving time, most of these areas shift to Mountain Daylight Time (UTC-6); Arizona is the notable exception and stays on MST year-round.
Plain English
It is the local clock time used in the Rocky Mountain region of the United States, running seven hours behind the worldwide reference time used in aviation.
Context Anchor
Seen in time zone discussions, flight planning, weather briefings, and any situation where a pilot must convert between local time and UTC.
Derivation
Named for the Rocky Mountains, which run through the region this time zone covers. The U.S. divided the country into time zones in 1883 to coordinate railroad schedules, and the Mountain Zone took the name of its geography.
Why Pilots Care
Accurate use prevents timing errors in departures, arrivals, and fuel calculations when crossing time zones.
Grounding Statement
Mountain Standard Time is the Mountain Time Zone’s normal clock setting, 7 hours earlier than UTC.
Intuition Check
Do not assume “Mountain” means any airport in mountainous terrain. Here it names a time zone. Also, “standard” does not mean “the time pilots always use”; aviation often uses UTC instead.
Example Sentence 1
Departure from Denver was scheduled for 0800 MST, which the pilot filed as 1500Z on the flight plan.
Example Sentence 2
After landing in Denver, the crew noted the arrival time in Mountain Standard Time for the logbook.