The Mountain Time Zone of North America keeps time by subtracting seven hours from Coordinated Universal Time (UTC-7) during the shortest days of autumn and winter, and by subtracting six hours during daylight saving time in the spring, summer, and early autumn (UTC-6). The clock time in this zone is based on the mean solar time of the 105th degree meridian west of the Greenwich Observatory. In the United States and Canada, this time zone is generically called Mountain Time (MT). Specifically, it is Mountain Standard Time (MST) when observing standard time (Winter), and Mountain Daylight Time (MDT) when observing daylight saving time. In Mexico this time is known as the Pacific Zone. The exact specification for the location of time zones and the dividing line between zones is set forth in the Code of Federal Regulations at 49 CFR 71.[1] The zone is one hour ahead of the Pacific Time Zone and one hour behind the Central Time Zone. In some areas, starting in 2007, the local time changes from MST to MDT at 02:00 LST to 03:00 LDT on the second Sunday in March and returns at 02:00 LDT to 01:00 LST on the first Sunday in November.
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Canada
The following provinces and areas are part of the Mountain Time Zone:
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- Alberta
- the Northwest Territories (except for Tungsten)
- the Kitikmeot Region of Nunavut
- portions of southeastern and northeastern British Columbia
- the area of Saskatchewan immediately surrounding the city of Lloydminster
Mexico
The following states are part of the Mountain Time Zone:
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- Baja California Sur
- Chihuahua
- Nayarit: just the Bahia de Banderas municipality uses the Central time zone.
- Sinaloa
- Sonora: always on MST - no daylight saving time
- Revillagigedo Islands (Colima): 3 of the 4 islands uses the Mountain Time Zone, Isla Socorro, San Benedicto Island and Roca Partida.
United States
The following states or areas are part of the Mountain Time Zone:
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- Arizona - always on MST - no daylight saving time except in Navajo reservation
- New Mexico
- Wyoming
- Utah
- Colorado
- Montana
- Idaho (except northern panhandle)
- Eastern Oregon/Malheur County
- the southwestern quadrant of North Dakota
- the western half of South Dakota
- the western third of Nebraska
- the two westernmost counties in Texas (Hudspeth, El Paso)
- four counties in Kansas (Greeley, Hamilton, Sherman, and Wallace)
- the Nevada towns of West Wendover and Jackpot
- the city of Kenton, Oklahoma
Arizona does not observe Daylight Saving Time. However, the Navajo Nation, the bulk of whose area is within Arizona, observes Daylight Saving Time throughout its territory. The Hopi Reservation, an enclave inside the Navajo Nation, does not observe Daylight Saving Time.
Major metropolitan areas
- Albuquerque, New Mexico
- Billings, Montana
- Boise, Idaho
- Calgary, Alberta
- Chihuahua, Chihuahua
- Ciudad Juárez, Chihuahua
- Colorado Springs, Colorado
- Cranbrook, British Columbia
- Denver, Colorado
- Edmonton, Alberta
- El Paso, Texas
- Fort St. John, British Columbia (no DST)
- Hermosillo, Sonora (no DST)
- La Paz, Baja California Sur
- Phoenix, Arizona (no DST)
- Salt Lake City, Utah
- Tucson, Arizona (no DST)
References
- ^ The specification for the Mountain Time Zone is set forth at 49 CFR 71.8, and is listed in Text and pdf formats.
The boundary between Central and Mountain is set forth at 49 CFR 71.7, and is listed in text and pdf formats. The boundary between Mountain and Pacific is set forth at 49 CFR 71.9, and is listed in text and pdf formats.
