MST — Mountain Standard Time

Mountain Standard Time (MST) is seven hours behind Coordinated Universal Time and covers the Rocky Mountain region of the United States and Canada. Major cities in this zone include Denver, Phoenix, Albuquerque, Salt Lake City, Calgary, and Edmonton. The zone takes its name from the Rocky Mountains, which run through its geographic center.

One of the most notable features of MST is that the state of Arizona does not observe daylight saving time, remaining on MST year-round. However, the Navajo Nation within Arizona does observe DST, creating a complex patchwork of time observance within the state. This decision dates back to 1968, when Arizona opted out of DST because the extra hour of evening sunlight was considered undesirable in the state's extreme desert heat.

For the rest of the Mountain time zone, daylight saving time shifts clocks forward to Mountain Daylight Time (MDT, UTC-6) from March through November. Denver, the largest city in the zone, is a major hub for the outdoor recreation industry and serves as the economic center of the Rocky Mountain West.