What is the difference between Mountain Time and Pacific Time?
Denver runs 1 hour ahead of Los Angeles. When it is 10:00 AM in LA, it is 11:00 AM in Denver. When it is 2:00 PM in Seattle, it is 3:00 PM in Calgary.
That 1-hour lead holds for most of the year. But the clock change dates introduce a short period each spring where the gap shrinks to zero. And the state that stays on standard time all year, Phoenix, Tucson, Mesa, behaves differently in summer.
Why does Mountain Time lead Pacific by 1 hour for most of the year?
From the first Sunday in November through the second Sunday in March, both zones are on standard time:
- Pacific Standard Time (PST) = UTC−8
- Mountain Standard Time (MST) = UTC−7
The offset difference is 1 hour. You add 1 hour to a Pacific time to get Mountain time.
From the second Sunday in March through the first Sunday in November, both zones are on daylight time:
The offset difference is still 1 hour. Same rule: Pacific + 1 hour = Mountain.
When does the 1-hour gap between Mountain and Pacific disappear?
The United States and Canada both switch to daylight saving on the second Sunday of March at 2:00 AM local time. But Mountain Time springs forward first.
Because the change happens at 2:00 AM local time in each zone, Pacific clocks are still on standard time for one hour after Mountain clocks have moved forward.
Example for 2026:
On Sunday, 8 March 2026, at 2:00 AM Mountain Time, clocks jump to 3:00 AM MDT. At that same moment, it is 1:00 AM Pacific Standard Time. For the next hour, until 2:00 AM Pacific Time, Mountain is 2 hours ahead of Pacific.
Then Pacific springs forward at 2:00 AM (which becomes 3:00 AM PDT), and the 1‑hour gap returns.
The same thing happens in reverse in November. Pacific falls back first, creating another hour where the gap is 2 hours.
For most people scheduling a meeting, these transition hours matter only if you are booking something at 1:00 AM, 3:00 AM Pacific on those specific Sundays.
Does Arizona stay on Mountain Standard Time when the rest of the zone moves to daylight?
Yes. The state does not observe daylight saving time. It stays on Mountain Standard Time (UTC−7) all year.
That means:
- In winter (November, March): Arizona matches the rest of Mountain Time (MST). Pacific is 1 hour behind.
- In summer (March, November): Arizona is on MST (UTC−7), while the rest of Mountain Time is on MDT (UTC−6). During this period, Arizona is 1 hour behind Denver, Calgary, and other Mountain‑observing places. Arizona matches Pacific Daylight Time, same clock reading, but a different zone name.
Practical consequences:
- A 2:00 PM call scheduled in “Mountain Time” in July means 1:00 PM in Phoenix but 2:00 PM in Denver.
- A 2:00 PM call scheduled in “Arizona time” in July means 2:00 PM in Phoenix but 3:00 PM in Denver.
Always specify the city or state, not just “Mountain Time”, when Arizona is involved. The Navajo Nation within the state does observe DST, creating a further local exception.
Quick reference: Mountain vs Pacific at a glance
| Situation | Pacific Time | Mountain Time (most of zone) | Arizona |
|---|---|---|---|
| Winter (standard time) | 10:00 AM PST | 11:00 AM MST | 11:00 AM MST |
| Summer (daylight time) | 10:00 AM PDT | 11:00 AM MDT | 10:00 AM MST |
| Spring‑forward Sunday (2:00 AM PT) | 2:00 AM PST | 3:00 AM MDT | 2:00 AM MST |
| Fall‑back Sunday (2:00 AM PT) | 2:00 AM PDT | 2:00 AM MST | 2:00 AM MST |
How do I convert Mountain Time to Pacific Time without mistakes?
- Check the date. If it is between the second Sunday of March and the first Sunday of November, most of Mountain is on MDT (UTC−6). If it is outside that window, Mountain is on MST (UTC−7).
- Check if Arizona is involved. If yes, the state is always UTC−7. Compare directly to Pacific: same offset in summer, 1 hour ahead in winter.
- When in doubt, use an IANA zone. For Denver, use
America/Denver. For Phoenix, useAmerica/Phoenix. For Los Angeles, useAmerica/Los_Angeles. The operating system or scheduling tool handles DST automatically.