How Does Daylight Saving Time Affect the Mountain Time Zone?
DST shifts Mountain Time from MST (UTC-7) in winter to MDT (UTC-6) in summer — with one major exception: Arizona.
MST vs MDT
| Abbreviation | Full Name | UTC Offset | Season |
|---|---|---|---|
| MST | Mountain Standard Time | UTC-7 | Winter |
| MDT | Mountain Daylight Time | UTC-6 | Summer |
2026 Switch Dates
- Spring forward: March 8, 2026 at 2:00 AM (MST to MDT)
- Fall back: November 1, 2026 at 2:00 AM (MDT to MST)
The Arizona Exception
Arizona (except the Navajo Nation) does not observe DST. It stays on MST (UTC-7) year-round. This means:
| Season | Colorado (Denver) | Arizona (Phoenix) | Difference |
|---|---|---|---|
| Winter | MST (UTC-7) | MST (UTC-7) | Same |
| Summer | MDT (UTC-6) | MST (UTC-7) | 1 hour apart |
States in the Mountain Time Zone
Colorado, Utah, Wyoming, Montana, Idaho (most), New Mexico, and parts of Kansas, Nebraska, North Dakota, South Dakota, and Texas (El Paso area).
Quick Answer
DST shifts Mountain Time from MST (UTC-7) to MDT (UTC-6) on March 8, 2026, and back on November 1, 2026. Arizona stays on MST year-round.