MDT – Mountain Daylight Time (Daylight Saving Time)

U.S. states using MDT in the summer and MST in the winter:

• Arizona - Navajo Nation only
• Colorado
• Idaho - most of the state except western counties Show

  Benewah, Bonner, Boundary, Clearwater, Kootenai, Latah, Lewis, Nez Perce, Shoshone and north part of Idaho

• Kansas - some western counties only Show

  Greeley, Hamilton, Sherman and Wallace

• Montana
• Nebraska - western counties Show

  Arthur, Banner, Box Butte, Chase, Cheyenne, Dawes, Deuel, Dundy, Garden, Grant, Hooker, Keith, Kimball, Morrill, Perkins, Scotts Bluff, Sheridan, and Sioux and the western part of Cherry

• New Mexico
• North Dakota - South-Western parts Show

  counties of Adams, Billings, Bowman, Golden Valley, Grant, Hettinger, Mercer, Slope and Stark, and southern parts of Dunn and McKenzie, most of Morton and Sioux counties

• Oregon - parts of Malheur county only Show

  rest of Oregon is PST/PDT

• South Dakota - western counties Show

  Bennett, Butte, Corson, Custer, Dewey, Fall River, Haakon, Harding, Jackson, Lawrence, Meade, Pennington, Perkins, Shannon, and Ziebach, and the western parts of Stanley

• Texas - a few counties in west Show

  El Paso and Hudspeth and part of Culberson

• Utah
• Wyoming

Canadian provinces/territories using MDT in the summer and MST in the winter:

• Alberta
• British Columbia - a few eastern communities Show

  Cranbrook, Golden, Invermere

• Northwest Territories
• Nunavut - Kugluktuk, Cambridge Bay only (Other parts use EST/EDT or EST only)
• Saskatchewan - only Lloydminster

Mexican states using MDT in the summer and MST in the winter:

• Baja California Sur
• Chihuahua
• Nayarit
• Sinaloa