Mountain Time Zone


The Mountain Time Zone of North America keeps time by subtracting seven hours from Coordinated Universal Time when standard time is in effect, and by subtracting six hours during daylight saving time.
In Canada, Mexico, and the United States, this time zone is generically called Mountain Time. Specifically, it is Mountain Standard Time when observing standard time, and Mountain Daylight Time 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 tiempo de la montaña or zona Pacífico. In the United States 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.
Most of 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 is the only part of Arizona that observes DST. Its territory lies mostly within Arizona but extends into Utah and New Mexico. Meanwhile, the Hopi Reservation, despite being completely surrounded by the Navajo Nation, does not observe DST, and neither do some Arizona state offices located within the Navajo Nation.
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 province and two territories are fully contained in the Mountain Time Zone:
  • Alberta
  • Northwest Territories
  • Yukon
On September 24, 2020, Yukon switched to the Mountain Standard Time year-round. 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.
One province is split between the Mountain Time Zone and the Pacific Time Zone:
  • British Columbia - northeastern and southeastern regions
One territory and one province are split between the Mountain Time Zone and the Central Time Zone:
As of October 30, 2022, Mexico abandoned daylight saving time, with certain exceptions.
The following states have an offset equal to Mountain Standard Time:
The following states have an offset equal to Mountain Daylight Time:

United States

Six states are fully contained in the Mountain Time Zone:
  • Colorado
  • Montana
  • New Mexico
  • Utah
  • Wyoming
  • Arizona
Three states are split between the Mountain Time Zone and the Pacific Time Zone. The following locations observe Mountain Time:
Five states are split between the Mountain Time Zone and the Central Time Zone. The following locations observe Mountain Time:
Alphabetical list of major cities located within the Mountain Time Zone. Cities in bold do not observe daylight saving time: