Mountain Time Zone
The Mountain Time Zone of North America keeps time by subtracting seven hours from Greenwich Mean Time, during the shortest days of autumn and winter (UTC−7), 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 at the 105th meridian west of the Greenwich Observatory. In the United States, the exact specification for the location of time zones and the dividing lines between zones is set forth in the Code of Federal Regulations at 49 CFR 71.[a]
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 (fall and winter), and Mountain Daylight Time (MDT) when observing daylight saving time (spring and summer). The term refers to the fact that the Rocky Mountains, which range from northwestern Canada to the US state of New Mexico, are located almost entirely in the time zone. In Mexico, this time zone is known as the Pacific Zone.
In some areas, starting in 2007, the local time changes from MST to MDT at 2 am MST to 3 am MDT on the second Sunday in March and returns at 2 am MDT to 1 am MST on the first Sunday in November.
Sonora in Mexico and most of Arizona in the United States do not observe daylight saving time, and during the spring, summer, and autumn months they are on the same time as Pacific Daylight Time. The Navajo Nation, most of which lies within Arizona, observes daylight saving time, although the Hopi Nation, as well as some Arizona state offices lying within the Navajo Nation, do not.
The largest city in the Mountain Time Zone is Ciudad Juárez, Chihuahua. The Phoenix metropolitan area is the largest metropolitan area in the zone; the largest metropolitan area that observes Mountain Daylight Time is the binational El Paso–Juárez area, closely followed by Denver, Colorado. TV broadcasting in the Mountain Time Zone is typically tape-delayed one hour, so that shows match the broadcast times of the Central Time Zone (i.e. prime time begins at 7 pm MT following the same order of programming as the Central Time Zone).
The following provinces and areas are part of the Mountain Time Zone:
The following states have the same time as Mountain Time Zone:
- Baja California Sur
- Nayarit: Except from the Bahía de Banderas municipality which uses the Central Time Zone.
- Sonora – no daylight saving time, always on MST.
- Revillagigedo Islands (Colima): three of the four islands have the same time as Mountain Time Zone, Isla Socorro, San Benedicto Island and Roca Partida.
The following states or areas are part of the Mountain Time Zone:
- Arizona – no daylight saving time, always on MST (winter time), except on the Navajo Nation.
- Idaho – southern half, south of the Salmon River
- Kansas – only the counties of Sherman, Wallace, Greeley and Hamilton, all of which border Colorado. The remaining three counties that border Colorado, Cheyenne, Morton and Stanton, observe Central Time, as do all other Kansas counties.
- Nebraska – western third
- Nevada – West Wendover, on the Utah border, is the only location in the state which legally observes Mountain Time. However, the towns of Jackpot, Jarbidge, Mountain City and Owyhee, while all legally within the Pacific Time Zone, locally observe the Mountain Time Zone due to proximity to and stronger connections with towns in nearby Idaho.
- New Mexico
- North Dakota – southwestern quadrant, southwest of the (Missouri River)
- Oregon – most of Malheur County, on the Idaho border
- South Dakota – western half
- Texas – the two westernmost counties (Hudspeth, El Paso)
Also, the unincorporated community of Kenton, Oklahoma, located in the extreme western end of the Oklahoma Panhandle, unofficially observes Mountain Time (as the nearest sizable 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. Additionally, western Culberson County, Texas unofficially observes Mountain Time.
- "49 CFR 71.8 Mountain zone". Code of Federal Regulations. Retrieved October 7, 2011.
- "49 CFR 71.7 Boundary line between central and mountain zones". Code of Federal Regulations. Retrieved October 7, 2011.
- "49 CFR 71.9 Boundary line between mountain and Pacific zones". Code of Federal Regulations. Retrieved October 7, 2011.
- Robbins, Ted (March 11, 2007). "Arizona Says No to Daylight-Saving Time". National Public Radio. Retrieved June 18, 2012.
- Delen Goldberg (July 2, 2011). "Nevada’s tiny town with a different time zone". Las Vegas Sun. Retrieved 2014-07-03.
West Wendover is the only town in Nevada that runs on Mountain Time. Jackpot, an even smaller town in Elko County, unofficially observes Mountain Time but is technically part of the Pacific Time Zone.(quote in slide 4)
- "Time Zone Exceptions and Oddities". Retrieved 2014-01-26.
- World time zone map
- U.S. time zone map
- History of U.S. time zones and UTC conversion
- Canada time zone map
- Time zones for major world cities
- The official U.S. time for the Mountain Time Zone (except Arizona)
- The official U.S. time for the Mountain Time Zone (Arizona)
- Official times across Canada
- Official times across Mexico
|Time zones in North America|
|Time zone||Hours from UTC: Standard time||Hours from UTC: Daylight saving time|
|Hawaii–Aleutian||–10||–9 (Alaska portion only)|
| Saint Pierre and Miquelon
and most of Greenland