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AST to MST: Atlantic Time to Mountain Time

3 hours behind AST

MST compared with AST, right now. Swap: MST to AST ⇄

ASTTuesday, November 3, 2026AST · UTC−4MSTTuesday, November 3, 2026MST · UTC−7

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AST to MST conversion table

For Tuesday, November 3, 2026. Rows where both places are inside 9 AM–5 PM are highlighted.

ASTMST
12:00 AM9:00 PM (previous day)
1:00 AM10:00 PM (previous day)
2:00 AM11:00 PM (previous day)
3:00 AM12:00 AM
4:00 AM1:00 AM
5:00 AM2:00 AM
6:00 AM3:00 AM
7:00 AM4:00 AM
8:00 AM5:00 AM
9:00 AM6:00 AM
10:00 AM7:00 AM
11:00 AM8:00 AM
12:00 PM9:00 AM
1:00 PM10:00 AM
2:00 PM11:00 AM
3:00 PM12:00 PM
4:00 PM1:00 PM
5:00 PM2:00 PM
6:00 PM3:00 PM
7:00 PM4:00 PM
8:00 PM5:00 PM
9:00 PM6:00 PM
10:00 PM7:00 PM
11:00 PM8:00 PM

About these time zones

AST: Atlantic Standard Time

Atlantic Time (AST/ADT). Nova Scotia, New Brunswick and Prince Edward Island (with daylight saving), plus Puerto Rico and much of the Caribbean, which stay on AST (UTC−4) all year.

Sunday, March 14, 2027: clocks go forward 1 hour at 2:00 AM local time (UTC−4 → UTC−3).

MST: Mountain Standard Time

Mountain Time (MST/MDT). Denver, Salt Lake City, Albuquerque, Boise and Calgary. MST is UTC−7; in summer most of the region uses MDT, UTC−6. Most of Arizona stays on MST all year.

Sunday, March 14, 2027: clocks go forward 1 hour at 2:00 AM local time (UTC−7 → UTC−6).

Questions about AST and MST time

What is the time difference between AST and MST?

The current difference is shown at the top of this page. AST uses Atlantic Standard Time (AST, UTC−4) as standard time and Atlantic Daylight Time (ADT, UTC−3) during daylight saving time; MST uses Mountain Standard Time (MST, UTC−7) as standard time and Mountain Daylight Time (MDT, UTC−6) during daylight saving time. The difference can change if only one side observes daylight saving time or if their clocks change on different dates. Choose your meeting date in the converter to check the applicable offset.

When it is 9:00 AM in AST, what time is it in MST?

On Tuesday, November 3, 2026, 9:00 AM in AST was 6:00 AM in MST. The conversion table above shows today’s values.

Do the clocks change in AST or MST?

AST: Sunday, March 14, 2027: clocks go forward 1 hour at 2:00 AM local time (UTC−4 → UTC−3). MST: Sunday, March 14, 2027: clocks go forward 1 hour at 2:00 AM local time (UTC−7 → UTC−6).

Is AST the same as ADT?

AST is the standard-time name and ADT the daylight-saving name for Atlantic Time. People often say AST all year; this converter uses the time actually in effect on the date you choose.

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