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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. 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 the United States and Canada, the Mountain Time 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 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, does observe DST, 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). ==Canada== (詳細は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 *however, these areas stay on Mountain Standard Time year-round, thus are on the same time as Pacific time zone areas for the majority of each year : *the area of Saskatchewan immediately surrounding the city of Lloydminster 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Mountain Time Zone」の詳細全文を読む スポンサード リンク
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