Mountain Time Zone (MT): States, Cities, and Key Facts
A Phoenix office schedules a call for 10 AM in July. A Denver team joins at 11 AM. Same zone, different clocks. That split-second confusion is the everyday reality of Mountain Time, the least populated continental US zone and the one where daylight saving fractures hardest. Here is what holds and what shifts.
What Is Mountain Time?
Mountain Time runs through a band of western North America anchored by the Rockies. It operates in two forms: Mountain Standard Time (MST), fixed at UTC-7, and Mountain Daylight Time (MDT), which pulls forward to UTC-6 during the warmer months. MT means UTC-7 in winter, UTC-6 in summer. The zone covers roughly a third of the continental US by area but only a sliver of its population.
Mountain Time Zone States: Full and Partial
Five states sit entirely inside Mountain Time. Another nine split their territory between Mountain and Central or Pacific.
Fully in Mountain Time:
| State | Notes |
|---|---|
| Colorado | Denver, Colorado Springs, Boulder |
| Montana | Billings, Missoula, Great Falls |
| New Mexico | Albuquerque, Santa Fe, Las Cruces |
| Utah | Salt Lake City, Provo, West Valley City |
| Wyoming | Cheyenne, Casper, Laramie |
Partially in Mountain Time:
| State | What splits it |
|---|---|
| Arizona | Most of the state stays on MST year-round. The Navajo Nation observes DST. See below. |
| Idaho | The southern part (Boise) is Mountain; the northern panhandle (Coeur d'Alene) is Pacific. |
| Kansas | Three counties in the far west (Greeley, Hamilton, Sherman) are Mountain; the rest is Central. |
| Nebraska | The western third (Scottsbluff, North Platte) is Mountain; the eastern two-thirds is Central. |
| Nevada | A small slice in the northeast (Jackpot, West Wendover) is Mountain; the rest is Pacific. |
| Oregon | Malheur County in the far east is Mountain; the rest is Pacific. |
| South Dakota | The western counties (Rapid City, the Black Hills) are Mountain; the east is Central. |
| Texas | Hudspeth and El Paso counties are Mountain; the rest of the state is Central. |
| North Dakota | Southwestern counties (including Bowman) are Mountain; the rest is Central. |
Nine states hold at least a piece of Mountain Time. Only five live there fully. Scheduling across a split state means confirming which side of the line the person occupies.
Major Cities in Mountain Time
- Denver, Colorado, The zone’s largest city. Financial and cultural anchor of the Rockies. Follows standard Mountain Time with DST.
- Phoenix, Arizona, But here is the catch: Phoenix stays on MST year-round. In winter it matches Denver. In the warm season, when Denver jumps to MDT, Phoenix holds at UTC-7, which equals Pacific Daylight Time. A New York call to Phoenix in July carries a 3-hour gap, not 2.
- Salt Lake City, Utah, Host of the 2002 Winter Olympics. Follows standard Mountain Time with DST.
- Albuquerque, New Mexico, The zone’s second-largest city. Follows standard Mountain Time with DST.
Other notable cities: El Paso, Texas, Missoula, Montana, and Cheyenne, Wyoming.
MST vs MDT: When Each Applies
The switch follows the same calendar as the rest of the US. On the second Sunday in March, clocks spring forward from MST to MDT. On the first Sunday in November, they fall back. During MDT (roughly March to November), Mountain Time sits at UTC-6. During MST (November to March), it returns to UTC-7.
The abbreviations carry weight. Saying “MST” in July is wrong. Saying “MDT” in January is wrong. Use “MT” if you are unsure, or say “Mountain Time” and let the season do the work.
Arizona’s No-DST Exception: MST Year-Round
Arizona is the big exception, and it trips up everyone. Most of the state skips daylight saving time. It stays on MST (UTC-7) all year. Why? The desert heat. Shifting an hour of daylight into the evening means hotter evenings and later sunsets in the warm season, which pushes air conditioning use up. So Arizona opts out.
The result: In winter, Arizona matches Denver. In the warm months, Arizona matches Los Angeles. People say “Arizona is on Pacific time in summer.” Technically false, practically true. Arizona is on MST, which happens to equal PDT.
One more layer: the Navajo Nation, covering northeastern Arizona, does observe DST. So if you are doing business with the Navajo Nation in the warm months, they run an hour ahead of the rest of the state. And inside the Navajo Nation sits the Hopi Reservation, which does not observe DST. A donut hole of time confusion. If your meeting touches any of these, confirm the exact location before sending an invite.
Quick Reference: Mountain Time UTC Offsets
| Season | Abbreviation | UTC Offset | Example |
|---|---|---|---|
| Winter (November to March) | MST | UTC-7 | Denver, Salt Lake City |
| Warm months (March to November) | MDT | UTC-6 | Denver, Salt Lake City |
| Year-round | MST | UTC-7 | Most of Arizona |
| Warm months only | MST (equals PDT) | UTC-7 | Most of Arizona, when Denver is on MDT |