Canada
The following provinces and areas are part of the Mountain Time Zone:
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- Alberta
- the Northwest Territories (except for Tungsten)
- most of 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: Except from the BahÃa de Banderas municipality which uses the Central time zone.
- Sonora - no daylight saving time, always on MST.
- Sinaloa
- 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 - no daylight saving time, always on MST, except in the Navajo Nation.
- Colorado
- Montana
- New Mexico
- Wyoming
- Utah
- Idaho - southern half, south of Salmon River
- Oregon - northern three quarters of Malheur County, on Idaho border
- North Dakota - southwestern quadrant, southwest of (Missouri River)
- South Dakota - western half
- Nebraska - western third
- Kansas - only the counties of Sherman, Wallace, Greeley and Hamilton, all of which border Colorado. The remaining three counties which border Colorado--Cheyenne, Morton and Stanton--observe Central Standard Time, as do all other Kansas counties.
- Texas - the two westernmost counties (Hudspeth, El Paso) and a portion of Culberson County
- Nevada - the border towns of West Wendover (near Utah) and Jackpot (near Idaho)
Also, the unincorporated community of Kenton, Oklahoma, located in the extreme western end of the Oklahoma Panhandle, unofficially observes Mountain Time (as the nearest sizeable towns are located in Colorado and New Mexico, both of which are in the Mountain Time Zone). However, the entire state of Oklahoma is officially in the Central Time Zone.
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.
