Mountain Time Zone

• 1. Introduction

  ›

  The Mountain Time Zone officially ends at the Nevada state line. Yet in Jackpot, Jarbidge, Mountain City, and Owyhee, clocks run on Mountain Time anyway, ignoring the official boundary entirely. Those four communities sit inside the Pacific Time Zone on paper, but nobody bothered to tell the people who live there.

  It raises an obvious question: if towns can simply opt out of their assigned zone, what actually holds this zone together across an entire continent? The zone reaches from the Yukon border in the north through six US states that belong to it completely. Dozens more states and provinces only partly belong, stretching down into much of Mexico. Some of those places refuse to change their clocks twice a year. Others changed their minds about which zone to belong to within the last few years.

  What follows traces the meridian that defines the zone and the places that quietly rewrote their own rules. It also visits the cities that anchor the zone, several of which cannot agree with their own neighbors on when to move the clock.

• 2. The Line At 105 Degrees

  ›

  Clocks in this zone run six hours behind Coordinated Universal Time each summer. Each winter they run seven hours behind, a one-hour swing known as daylight saving time. Across Canada, Mexico, and the United States, people simply call it Mountain Time, shortened to MT. The more formal names split by season: Mountain Standard Time during winter, Mountain Daylight Time during summer.

  The 105th meridian west of the Greenwich Observatory sets the zone's mean solar time. That line runs through the Rocky Mountains, which is where the zone gets its name.

  In the United States, Title 49 of the Code of Federal Regulations, part 71, spells out where this zone ends and the next begins. Not every place under that meridian bothers to spring forward, though.

• 3. Who Skips The Clock Change

  ›

  Arizona does not spring forward each year. For most of spring, summer, and autumn, its clocks match Pacific Daylight Time instead of the rest of the Mountain zone. The Navajo Nation, which crosses into the state, observes daylight saving time anyway, splitting Arizona's clocks in two.

  British Columbia takes a different approach entirely, keeping permanent daylight saving time in the Pacific Time Zone, which works out to year-round Mountain Standard Time. On the 8th of March 2026, most of the province adopted UTC-7 permanently, though it kept calling its clock Pacific Time. Only the southeastern corner near the Alberta border still shifts its clocks, running UTC-6 in summer and UTC-7 in winter.

  Yukon rewrote its own clock rules earlier still, and in a different way entirely.

• 4. Redrawn Borders In Canada

  ›

  On the 24th of September 2020, Yukon abandoned its daylight-saving schedule and switched to Mountain Standard Time year-round. Before that, the territory ran on the Pacific Time Zone, dropping to UTC-8 each winter and rising to UTC-7 each summer. The switch means Yukon and Alberta share identical clocks every winter, while Alberta pulls an hour ahead each summer when it moves to daylight time.

  Alberta, British Columbia, the Northwest Territories, and Yukon are the two provinces and two territories that sit entirely inside the Mountain Time Zone.

  Two more Canadian regions straddle the border with the Central Time Zone: Nunavut's Kitikmeot Region, and the area around Lloydminster in Saskatchewan. Mexico redrew its own clock map only two years after Yukon did.

• 5. Mexico's Two Zones

  ›

  On the 30th of October 2022, Mexico abandoned daylight saving time almost entirely, keeping only a few exceptions near its northern border.

  Baja California Sur, Sonora, and Sinaloa now sit permanently in what Mexico calls the Zona Pacifico, matching Mountain Standard Time all year. Nayarit joins them too, except for the municipality of Bahía de Banderas, which instead follows the Central Time Zone. Chihuahua mostly follows suit, but its northwestern border towns, Janos, Ascensión, Juárez, Guadalupe, and Práxedis Gilberto Guerrero, still observe daylight saving time.

  Off Mexico's Pacific coast, three of the four Revillagigedo Islands, Socorro, San Benedicto, and Roca Partida, keep Mountain Time even though they belong to Colima.

  Most of central and southern Mexico instead falls into the Zona Centro, matching Mountain Daylight Time or Central Standard Time depending on the season. That zone stretches from Mexico City and Jalisco to Michoacán and Veracruz, covering most of the country's central and southern states. North of the border, the United States carves out its own exceptions state by state.

• 6. America's Patchwork

  ›

  Colorado, Montana, New Mexico, Utah, Wyoming, and Arizona are the only six states that sit entirely inside the Mountain Time Zone.

  Idaho splits between zones. Its southern half, plus the part of Idaho County south of the Salmon River, runs on Mountain Time. Oregon contributes the majority of Malheur County, and Nevada contributes the single town of West Wendover.

  Five more states split the difference with the Central Time Zone instead. Kansas contributes Sherman, Wallace, Greeley, and Hamilton counties; Nebraska contributes its western third; and South Dakota contributes its western half. North Dakota's Adams, Billings, Bowman, Golden Valley, Grant, Hettinger, Slope, and Stark counties keep Mountain Standard Time. McKenzie, Dunn, and Sioux counties are split down the middle. Texas rounds out the list with El Paso, Hudspeth, and the northwestern part of Culberson County.

  For all this border-hopping, one desert city outgrew every other in the zone.

• 7. The Biggest Cities

  ›

  Phoenix, Arizona, is the largest city anywhere in the Mountain Time Zone, and its metropolitan area is the zone's largest as well. That metro area includes Chandler, Gilbert, Glendale, Mesa, Peoria, Surprise, and Tempe, all clustered around Phoenix itself.

  Juárez, Chihuahua, holds a different title: it is the largest city in the entire zone that actually observes daylight saving time.

  Denver anchors its own cluster too, Metropolitan Denver, spreading across Arvada, Aurora, Centennial, Lakewood, and Westminster around the Colorado capital. Salt Lake City leads a corridor called the Wasatch Front, joined by Orem, Provo, West Jordan, and West Valley City.

  Calgary and Edmonton anchor Alberta's share of the zone. Albuquerque, Boise, Cheyenne, Colorado Springs, and Tucson round out the major cities across the US and Canada. On the same alphabetical list, Vancouver, British Columbia, appears too, a Pacific Time city that still gets counted among the zone's own. The roster ends, fittingly, at Yuma, Arizona, the last name on a list running from Alberta to Sinaloa's Pacific coast.