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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). 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. 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, and Mountain Daylight Time (MDT) when observing daylight saving time. The term refers to the Rocky Mountains, which range from British Columbia to New Mexico. In Mexico, this time zone is known as the or ("Pacific Zone"). In the US and Canada, the Mountain Time Zone is to the east of the Pacific Time Zone and to the west of the Central Time Zone. In some areas, starting in 2007, the local time changes from MST to MDT at 2am MST to 3am MDT on the second Sunday in March and returns at 2am MDT to 1am 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 but extends into Utah and New Mexico (which do observe DST), does observe DST, although the Hopi Reservation, 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; the Phoenix metropolitan area is the largest metropolitan area in the zone.

Canada

Only one Canadian province is fully contained in the Mountain Time Zone: *Alberta One province and one territory are split between the Mountain Time Zone and the Pacific Time Zone: *British Columbia – northeastern and southeastern regions *Northwest TerritoriesTungsten One territory and one province are split between the Mountain Time Zone and the Central Time Zone *Nunavut: Kitikmeot Region *Saskatchewan: Lloydminster and vicinity On September 24, 2020, Yukon switched to a new time zone called Yukon Standard Time, which is UTC−7 year roundthe same as Mountain Standard Time. Therefore clocks in Yukon and Alberta are the same in the winter, and Alberta is one hour ahead in summer. Previously the territory had used the Pacific Time Zone with daylight saving time: UTC−8 in winter and UTC−7 in summer.http://www.gov.yk.ca/legislation/regs/oic2020_125.pdf

Mexico

The following states have the same time as Mountain Time Zone: :*Baja California Sur :*Chihuahua :*Nayarit: Except for the Bahía de Banderas municipality, which uses the Central Time Zone. :*Sonora – no daylight saving time, always on MST. :*Sinaloa :*Revillagigedo Islands (Colima): three of the four islands have the same time as Mountain Time Zone, Isla Socorro, San Benedicto Island and Roca Partida.

United States

Six states are fully contained in the Mountain Time Zone: *Colorado *Montana *New Mexico *Utah *Wyoming *Arizona (does not use 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 *Oregon: the majority of Malheur County *Nevada: West Wendover; other small towns in Elko County observe it unofficially. Five 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 third *North Dakota: the SW corner counties (Adams, Billings, Bowman, Golden Valley, Grant, Hettinger, Slope, Stark) observe MST. The counties of McKenzie, Dunn, and Sioux are split. *South Dakota: western half *Texas: El Paso and Hudspeth counties

See also

* Effects of time zones on North American broadcasting

Notes



References


World time zone map



History of U.S. time zones and UTC conversion





Official times across Canada

Official times across Mexico



U.S. time map
{{North American time zones Category:Time zones Category:Time in Canada Category:Time in Mexico Category:Time zones in the United States