|Mountain Time Zone|
MST or UTC−07:00
|23:05, January 7, 2020 MST|
|Observance of DST|
|DST is observed in some of this time zone.|
The Mountain Time Zone of North America keeps time by subtracting seven hours from Coordinated Universal Time (UTC) when standard time 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 how 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 Zona Pacífico (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 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 but extends into Utah and New Mexico (which do observe DST), 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 Phoenix, Arizona; the Phoenix metropolitan area is the largest metropolitan area in the zone; the next largest metropolitan area that observes Mountain Time is Denver, closely followed by the El Paso–Juárez area.
Only one Canadian province is fully contained in the Mountain Time Zone:
One province and one territory are split between the Mountain Time Zone and the Pacific Time Zone:
One territory and one province are split between the Mountain Time Zone and the Central Time Zone
The following states have the same time as Mountain Time Zone:
Five states are fully contained in the Mountain Time Zone:
Three states are split between the Mountain Time Zone and the Pacific Time Zone. The following locations observe Mountain Time:
Six states are split between the Mountain Time Zone and the Central Time Zone. The following locations observe Mountain Time:
The history of standard time in the United States began November 18, 1883, when United States and Canadian railroads instituted standard time in time zones. Before then, time of day was a local matter, and most cities and towns used some form of local solar time, maintained by some well-known clock. The new standard time system was not immediately embraced by all.
The North American Central Time Zone (CT) is a time zone in parts of Canada, the United States, Mexico, Central America, some Caribbean Islands, and part of the Eastern Pacific Ocean.
The Eastern Time Zone (ET) is a time zone encompassing part or all of 22 states in the eastern part of the contiguous United States, parts of eastern Canada, the state of Quintana Roo in Mexico, Panama in Central America, and certain Caribbean and Atlantic islands, along with certain countries and parts of countries in South America. Places that use Eastern Standard Time (EST) when observing standard time (autumn/winter) are five hours behind Coordinated Universal Time (UTC−05:00).
The Pacific Time Zone (PT) is a time zone encompassing parts of western Canada, the western United States, and western Mexico. Places in this zone observe standard time by subtracting eight hours from Coordinated Universal Time (UTC−08:00). During daylight saving time, a time offset of UTC−07:00 is used.
Time in the United States, by law, is divided into nine standard time zones covering the states, territories and other US possessions, with most of the United States observing daylight saving time (DST) for approximately the spring, summer, and fall months. The time zone boundaries and DST observance are regulated by the Department of Transportation. Official and highly precise timekeeping services (clocks) are provided by two federal agencies: the National Institute of Standards and Technology (NIST) ; and the United States Naval Observatory (USNO). The clocks run by these services are kept synchronized with each other as well as with those of other international timekeeping organizations.
The Uniform Time Act of 1966, Pub.L. 89–387, 80 Stat. 107, enacted April 13, 1966, was a Law of the United States to "promote the adoption and observance of uniform time within the standard time zones" prescribed by the Standard Time Act of 1918. Its intended effect was to simplify the official pattern of where and when daylight saving time (DST) is applied within the U.S. Prior to this law, each state had its own scheme for when DST would begin and end, and in some cases, which parts of the state should use it.
UTC−05:00 is an identifier for a time offset from UTC of −05:00. In North America, it is observed in the Eastern Time Zone during standard time, and in the Central Time Zone during the other eight months. The western Caribbean uses it year round.
UTC−07:00 is an identifier for a time offset from UTC of −07:00. In North America, it is observed in the Mountain Time Zone during standard time, and in the Pacific Time Zone during the other 8 months. A few places use it year-round.
UTC−06:00 is an identifier for a time offset from UTC of −06:00. In North America, it is observed in the Central Time Zone during standard time, and in the Mountain Time Zone during the other eight months. Several Latin American countries and a few other places use it year round.
Canada is divided into six time zones, based on proposals by Scottish Canadian railway engineer Sir Sandford Fleming, who pioneered the use of the 24-hour clock, the world's time zone system, and a standard prime meridian. Most of Canada operates on standard time from the first Sunday in November to the second Sunday in March and daylight saving time the rest of the year.
Tarkio is an unincorporated community in Montana, located in Mineral County. Tarkio falls in Mountain Time Zone (MST/MDT) and observes daylight saving time.
The Chamorro Time Zone, formerly the Guam Time Zone, is a United States time zone which observes standard time ten hours ahead of Coordinated Universal Time (UTC+10:00). The clock time in this zone is based on the mean solar time of the 150th meridian east of the Greenwich Observatory.
Mexico uses four main time zones since February 2015. Most of the country observes Daylight Saving Time.
Daylight saving time in the United States is the practice of setting the clock forward by one hour during the warmer part of the year, so that evenings have more daylight and mornings have less. Most areas of the United States and Canada observe daylight saving time (DST), the exceptions being Arizona, Hawaii, and the overseas territories of American Samoa, Guam, the Northern Mariana Islands, Puerto Rico, and the United States Virgin Islands. The Uniform Time Act of 1966 established the system of uniform Daylight Saving Time throughout the US.
Nunavut is divided into three time zones: Eastern, Central and Mountain.
Milner is an unincorporated community located in Routt County, Colorado, United States. The elevation is 6,522 feet above sea level. Milner lies in the Mountain Time Zone (MST/MDT) and observes daylight saving time. The settlement is located along U.S. Hwy 40 between the nearby communities of Craig and Steamboat Springs.
The Standard Time Act of 1918, also known as the Calder Act, was the first United States federal law implementing Standard time and Daylight saving time in the United States. It authorized the Interstate Commerce Commission to define each time zone.
Daylight saving time (DST) is observed in all ten Canadian provinces and three territories. However, there are exceptions: most of Saskatchewan observes Central Standard Time year-round and most of the territory of Nunavut, with its three time zones, observes daylight saving time. Under the Canadian Constitution, laws related to timekeeping are a provincial or territorial matter.
Time in Arizona, as in all US states, is regulated by the United States Department of Transportation.
Coalwood is an unincorporated community in northern Powder River County, Montana, United States. It lies along Montana Highway 59 23.5 miles (37.8 km) north of the town of Broadus, the county seat of Powder River County.
Time zones in North America
|Time zone||Hours from UTC: Standard time||Hours from UTC: Daylight saving time|
|Hawaii–Aleutian (in Hawaii)||–10||–10|
|Hawaii–Aleutian (in Alaska)||–10||–9|
|Pacific (in Alaska)||–8||–8|
|Pacific (other states/provinces)||–8||–7|
|Mountain (Arizona, Sonora, and Northeastern British Columbia only)||–7||–7|
|Mountain (other states/provinces)||–7||–6|
|Central (Saskatchewan only)||–6||–6|
|Central (other states/provinces)||–6||–5|
|Eastern (parts of Nunavut and the Caribbean)||–5||–5|
|Eastern (other states/provinces)||–5||–4|
|Atlantic (Natashquan River)||–4||–4|
|Atlantic (other states/provinces)||–4||–3|
| Saint Pierre and Miquelon |
and most of Greenland