The Mountain Time Zone of North America keeps time by subtracting seven hours from Coordinated Universal Time (UTC) when standard time (UTC−07:00) is in effect, and by subtracting six hours during daylight saving time (UTC−06:00).
In Canada and the United States, this time zone is generically called Mountain Time (MT). Specifically, it is Mountain Standard Time (MST) when observing standard time, and Mountain Daylight Time (MDT) when observing daylight saving time. The term refers to the Rocky Mountains.
Baja California Sur, Sinaloa, and Sonora in Mexico, and most of Arizona in the United States, do not observe daylight saving time (DST), and during the spring, summer, and autumn months they are on the same time as Pacific Daylight Time. The Canadian province of British Columbia and Yukon Territory observe permanent daylight saving time in the Pacific Time Zone, which is equivalent to year-round Mountain Standard Time.
The largest city in the Mountain Time Zone is Phoenix, Arizona; the Phoenix metropolitan area is the largest metropolitan area in the zone. The largest city that observes daylight saving time is Juárez, Chihuahua, Mexico.
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.
Canada
One territory is fully contained in the Mountain Time Zone: Yukon (no DST)
One province is split between the Mountain Time Zone and the Central Time Zone: British Columbia – all except Regional District of East Kootenay, Town of Golden, and Columbia-Shuswap Regional District Area A
One territory is split between the Mountain Time Zone, the Central Time Zone, and the Eastern Time Zone: Nunavut – Kitikmeot Region
On September 24, 2020, Yukon switched to the Mountain Standard Time year-round. Previously, the territory had used the Pacific Time Zone with daylight saving time: UTC−8 in winter and UTC−7 in summer.
On March 8, 2026, most of British Columbia in the Pacific Time Zone adopted UTC−7 year-round but continue to call their time zone "Pacific Time" with a new abbreviation of "PCT".
Alberta observed Mountain Time with daylight saving until 2026, when it switched to Central Standard Time (UTC−06:00) year-round. The western half of Saskatchewan observed Mountain Time without daylight saving until 1972 when it joined the rest of the province in Central Standard Time.
Following Alberta's switch to Central Standard Time year-round, on August 14, 2026, the Regional District of East Kootenay in southeastern BC also switched to Central Standard Time year-round from Mountain Time with daylight saving to maintain its alignment with Alberta. The Town of Golden and Columbia-Shuswap Regional District, which were also previously on Mountain Time with daylight saving time, originally adopted permanent standard time on September 1, 2026, planning to sync the localities with the rest of BC besides the Regional District of East Kootenay by moving an hour back on November 1, 2026. However, on September 22, 2026, this decision was reversed and the two municipalities opted to adopt Central Standard Time year-round, retaining continuity with Alberta and East Kootenay.
Similarly, the Northwest Territories observed Mountain Time with daylight saving until 2026 before switching to Central Standard Time year-round on August 21, 2026.
Mexico
As of October 30, 2022, Mexico abandoned daylight saving time, with certain exceptions. The following states have an offset equal to Mountain Standard Time, there called the (lit. 'Pacific Zone'):
Baja California Sur Nayarit: except for the Bahía de Banderas municipality, which uses the Central Time Zone. Sonora Sinaloa Chihuahua: Observes Daylight Savings Time, only in northwestern border municipalities (Janos, Ascensión, Juárez, Guadalupe, and Práxedis Gilberto Guerrero) Revillagigedo Islands (Colima): three of the four islands have the same time as Mountain Time Zone: Socorro Island, San Benedicto Island and Roca Partida.
The following states have an offset equal to Mountain Daylight Time or Central Standard Time, there called the (Central Zone):
Aguascalientes Campeche Chihuahua, except for the northwestern border area (which follows MST/MDT) and northeastern border area (follows CST/CDT) Ciudad de México Coahuila, except for northern border areas (CST/CDT) Colima, except all of the Revillagigedo Islands. Chiapas Durango Guanajuato Guerrero Hidalgo Jalisco México Michoacán Morelos Nuevo León, except for northern border areas (CST/CDT) Oaxaca Puebla Querétaro San Luis Potosí Tabasco Tamaulipas, except for northern border areas (CST/CDT) Tlaxcala Veracruz Yucatán Zacatecas Municipality of Bahía de Banderas in Nayarit
United States
Six states are fully contained in the Mountain Time Zone: Colorado Montana New Mexico Utah Wyoming Arizona (does not observe daylight saving time except for Navajo Nation)
Three states are split between the Mountain Time Zone and the Pacific Time Zone. The following locations observe Mountain Time: Idaho: Southern Idaho and the portion of Idaho County south of the Salmon River Oregon: the majority of Malheur County Nevada: West Wendover The communities of Jackpot, Jarbidge, Mountain City, and Owyhee unofficially observe Mountain Time, although they are officially within the Pacific Time Zone.
Six states are split between the Mountain Time Zone and the Central Time Zone. The following locations observe Mountain Time: Kansas: Sherman, Wallace, Greeley and Hamilton counties Nebraska: western one third North Dakota: the southwest corner counties (Adams, Billings, Bowman, Golden Valley, Grant, Hettinger, Slope, Stark) observe MST. The counties of McKenzie, Dunn, and Sioux are split. Oklahoma: Kenton South Dakota: western half Texas: El Paso, Hudspeth, and northwestern Culberson counties
Major metropolitan areas Alphabetical list of major cities located within the Mountain Time Zone. Cities in bold do not observe daylight saving time:
Albuquerque, New Mexico Billings, Montana Boise, Idaho Boulder, Colorado Casper, Wyoming Cheyenne, Wyoming Ciudad Juárez, Chihuahua Ciudad Obregón, Sonora Colorado Springs, Colorado Culiacán, Sinaloa Metropolitan Denver Arvada, Colorado Aurora, Colorado Centennial, Colorado Denver, Colorado Lakewood, Colorado Westminster, Colorado El Paso, Texas Flagstaff, Arizona Fort Collins, Colorado Greeley, Colorado Hermosillo, Sonora La Paz, Baja California Sur Lake Havasu City, Arizona Las Cruces, New Mexico Los Mochis, Sinaloa Mazatlán, Sinaloa Missoula, Montana Nogales, Sonora Metropolitan Phoenix Chandler, Arizona Gilbert, Arizona Glendale, Arizona Mesa, Arizona Peoria, Arizona Phoenix, Arizona Surprise, Arizona Tempe, Arizona Pueblo, Colorado Rapid City, South Dakota St. George, Utah San Luis Río Colorado, Sonora Tepic, Nayarit Tucson, Arizona Wasatch Front Orem, Utah Provo, Utah Salt Lake City, Utah Sandy, Utah West Jordan, Utah West Valley City, Utah Vancouver, British Columbia Yuma, Arizona
See also Effects of time zones on North American broadcasting
Notes
References
External links World time zone map U.S. time zone map History of U.S. time zones and UTC conversion Canada time zone map Official times across Mexico Canada time map U.S. time map