Mountain Time Zone

This article is about the time zone with daylight change in North America. For the static time zone, see UTC−07.

  MST or UTC−7

The Mountain Time Zone of North America keeps time by subtracting seven hours from Coordinated Universal Time, also known as 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 of the 105th 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 (spring, summer, fall). 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 is known as the Pacific Zone. In the USA, 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.^a

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.

Most of Arizona does not observe daylight saving time, and during the spring, summer, and autumn months it is on the same time as Pacific Daylight Time, though it is still called Mountain Standard Time in Arizona. The Navajo Nation, most of which lies within Arizona, does observe 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 Phoenix, Arizona, and its metropolitan area is the largest in the zone.

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 7:00 p.m. MT following the same order of programming as the other two time zones).

Canada

Main article: Time in Canada

The following provinces and areas are part of the Mountain Time Zone:

• 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

Main article: Time in Mexico

The following states have the same time as Mountain Time Zone:

• Baja California Sur
• Chihuahua
• Nayarit: Except from the Bahía 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 have the same time as Mountain Time Zone, Isla Socorro, San Benedicto Island and Roca Partida.

United States

Main article: Time in the United States

The following states or areas are part of the Mountain Time Zone:

• Arizona - no daylight saving time, always on MST (winter time), 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.

Tz database

See also: List of tz database time zones

US     +394421−1045903 America/Denver   Colorado
US     +433649−1161209 America/Boise    south Idaho & east Oregon
US     +364708−1084111 America/Shiprock Navajo
US     +332654−1120424 America/Phoenix  Arizona

Major metropolitan areas

• Albuquerque, New Mexico
• Billings, Montana
• Boise, Idaho
• Calgary, Alberta
• Chihuahua, Chihuahua
• Ciudad Juárez, Chihuahua
• Cranbrook, British Columbia
• Edmonton, Alberta
• El Paso, Texas
• Fort McMurray, Alberta
• Front Range, Colorado/Wyoming — north to south:
  • Cheyenne, Wyoming
  • Fort Collins, Colorado
  • Denver, Colorado
  • Colorado Springs, Colorado
  • Pueblo, Colorado
• La Paz, Baja California Sur
• Las Cruces, New Mexico
• Lethbridge, Alberta
• Phoenix, Arizona*
• Rapid City, South Dakota
• Red Deer, Alberta
• Santa Fe, New Mexico
• Tucson, Arizona
• Wasatch Front, Utah — north to south:
  • Ogden
  • Salt Lake City
  • Provo
• Yellowknife, Northwest Territories

*- Largest city in time zone

See also

• Effects of time on North American broadcasting

Notes

^a The specification for the Mountain Time Zone in the United States is set forth at 49 CFR 71.8.^[1][2] The boundary between Central and Mountain time zones is set forth at 49 CFR 71.7,^[3][4] and the boundary between Mountain and Pacific time zones is set forth at 49 CFR 71.9.^[5][6]

References

1. ^ "49 CFR 71.8 Mountain zone" (txt), Code of Federal Regulations, http://edocket.access.gpo.gov/cfr_2008/octqtr/49cfr71.8.htm, retrieved 2011 October 07 
2. ^ "49 CFR 71.8 Mountain zone" (pdf), Code of Federal Regulations, http://edocket.access.gpo.gov/cfr_2008/octqtr/pdf/49cfr71.8.pdf, retrieved 2011 October 07 
3. ^ "49 CFR 71.7 Boundary line between central and mountain zones", Code of Federal Regulations, http://edocket.access.gpo.gov/cfr_2008/octqtr/49cfr71.7.htm, retrieved 2011 October 07 
4. ^ "49 CFR 71.7 Boundary line between central and mountain zones" (pdf), Code of Federal Regulations, http://edocket.access.gpo.gov/cfr_2008/octqtr/pdf/49cfr71.7.pdf, retrieved 2011 October 07 
5. ^ "49 CFR 71.9 Boundary line between mountain and Pacific zones", Code of Federal Regulations, http://edocket.access.gpo.gov/cfr_2008/octqtr/49cfr71.9.htm, retrieved 2011 October 07 
6. ^ "49 CFR 71.9 Boundary line between mountain and Pacific zones" (pdf), Code of Federal Regulations, http://edocket.access.gpo.gov/cfr_2008/octqtr/pdf/49cfr71.9.pdf, retrieved 2011 October 07 

Sources

• 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