Here’s your go-to guide on the Mountain Time Zone—what it is, where it applies, and how it affects daily life, travel, and timekeeping across North America.

Table of Contents

What Is the Mountain Time Zone?

The Mountain Time Zone (MT) is one of nine standard time zones used in the United States and its territories. It primarily covers the western half of the central U.S. and gets its name from the Rocky Mountains, which run through much of the region.

Introduced in the late 19th century along with other U.S. time zones, Mountain Time is used by a mix of urban hubs and vast rural landscapes. It’s generally UTC-7 (MST) and UTC-6 (MDT) during daylight saving time.

Time Zone History & Background

Before time zones, Americans used the sun to tell time. Noon was when the sun reached its highest point locally, so time varied from town to town.

  • This system created confusion—especially for the growing railroad industry.
  • In response, railroads introduced over 100 local time standards, which still caused complications.
  • Finally, on November 18, 1883, four U.S. time zones were officially adopted:
    • Eastern
    • Central
    • Mountain
    • Pacific
  • Additional zones like Alaska, Hawaii, and Samoa were added later.

Mountain Time Explained

Mountain Time operates in two variations throughout the year:

Time Format Months Used UTC Offset
Mountain Standard Time (MST) November to March UTC -7
Mountain Daylight Time (MDT) March to November (DST) UTC -6

Note: Arizona and Sonora, Mexico do not observe daylight savings and remain on MST year-round.

Where Is Mountain Time Used?

The Mountain Time Zone is used widely across North America:

Fully Covered U.S. States

  • Colorado
  • Montana
  • New Mexico
  • Utah
  • Wyoming

Partially Covered U.S. States

  • Arizona (no DST)
  • Nevada
  • Texas
  • Kansas
  • Idaho
  • Oregon
  • Nebraska
  • Oklahoma
  • North Dakota
  • South Dakota

International Regions

  • Mexico: Several northern states and islands
  • Canada: All of Alberta, and parts of British Columbia, Northwest Territories, Saskatchewan, and Nunavut

Major Cities in Mountain Time

  • Phoenix, Arizona (largest metro, no DST)
  • Denver, Colorado
  • El Paso, Texas

Daylight Saving Time in the Mountain Time Zone

Daylight Saving Time (DST) was introduced in 1966 with the Uniform Time Act to help save energy and extend daylight during warmer months.

  • Original DST dates: First Sunday in April to last Sunday in October
  • Current schedule (since 2005): Second Sunday in March to first Sunday in November
  • Arizona and Sonora, Mexico do not observe DST

The shift to Mountain Daylight Time (MDT) each spring helps align working hours with daylight, but not all Mountain Time regions choose to participate.

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