What is the difference between MST and MDT?

MDT is daylight saving time: clocks move forward one hour in spring. MST (UTC−7) applies from the first Sunday in November to the second Sunday in March; MDT (UTC−6) applies the rest of the year.

When does MDT start and end?

In the US, daylight saving time starts at 2:00 AM on the second Sunday in March and ends at 2:00 AM on the first Sunday in November.

Is it MST or MDT right now?

Between mid-March and early November it is MDT; the rest of the year it is MST. Many people write “MT” (e.g. ET, CT) to mean whichever is currently in effect.

MST to MDT Time

Effortlessly convert Mountain Standard Time (MST) to Mountain Daylight Time (MDT) to ensure smooth coordination of meetings, online webinars, and appointments during daylight saving transitions.

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Updated Sep 2026

In short

MDT is 1 hour ahead of MST. MST (UTC−7) and MDT (UTC−6) are the winter and summer times of the same US region, so a clock showing 10:20 PM MST reads 11:20 PM MDT.

How it works

MST and MDT are the same place — US Mountain — at different times of year. MST is standard time, used from early November to mid-March; MDT is daylight saving time, used from mid-March to early November. They are exactly one hour apart.

Take the MST time.
Add one hour.
That is the same moment written as MDT.

Clocks go forward on the second Sunday in March at 2 a.m. local time and back on the first Sunday in November. On those two days one hour is skipped or repeated, which is why appointment times around 2 a.m. can look strange.

Writing “Mountain Time” or the city name avoids the problem entirely: it means whichever of the two is in force on that date. The converter above does that automatically.

Examples

The same moment, written both ways:

MST and MDT
MST	MDT
09:00	10:00
12:00	13:00
17:30	18:30
23:00	00:00 (next day)

Only one of the two labels is correct on any given date, so a meeting invite in MST during summer is usually a mistake for MDT.

MST to MDT Time: frequently asked questions

What is the difference between MST and MDT?: MDT is daylight saving time: clocks move forward one hour in spring. MST (UTC−7) applies from the first Sunday in November to the second Sunday in March; MDT (UTC−6) applies the rest of the year.
When does MDT start and end?: In the US, daylight saving time starts at 2:00 AM on the second Sunday in March and ends at 2:00 AM on the first Sunday in November.
Is it MST or MDT right now?: Between mid-March and early November it is MDT; the rest of the year it is MST. Many people write “MT” (e.g. ET, CT) to mean whichever is currently in effect.