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DateAlmanac

What is AST in MST?

Mountain Time is 3 hours behind

Atlantic Time is on UTC−4:00 and Mountain Time is on UTC−7:00 right now. That gap holds all year, because both zones change their clocks on the same dates.

Convert a time

MST — Mountain Time

1:00 am

MST, Sat

Time in Halifax
4:28:53 AM
Time in Denver
1:28:53 AM
Difference
−3 h
Next clock change
March 14, 2027

Daylight saving

Atlantic Time

Sunday, March 14, 2027

Clocks go forward one hour — 2:00 am becomes 3:00 am local time, and the zone is on ADT after that.

Mountain Time

Sunday, March 14, 2027

Clocks go forward one hour — 2:00 am becomes 3:00 am local time, and the zone is on MDT after that.

AST to MST conversion table

Every hour of Saturday, November 7, 2026, converted from Atlantic Time to Mountain Time. 3 of the 24 hours fall on a different calendar day in Denver, which is marked.

12:00 am AST
9:00 pm MST−1 day
1:00 am AST
10:00 pm MST−1 day
2:00 am AST
11:00 pm MST−1 day
3:00 am AST
12:00 am MST
4:00 am AST
1:00 am MST
5:00 am AST
2:00 am MST
6:00 am AST
3:00 am MST
7:00 am AST
4:00 am MST
8:00 am AST
5:00 am MST
9:00 am AST
6:00 am MST
10:00 am AST
7:00 am MST
11:00 am AST
8:00 am MST
12:00 pm AST
9:00 am MST
1:00 pm AST
10:00 am MST
2:00 pm AST
11:00 am MST
3:00 pm AST
12:00 pm MST
4:00 pm AST
1:00 pm MST
5:00 pm AST
2:00 pm MST
6:00 pm AST
3:00 pm MST
7:00 pm AST
4:00 pm MST
8:00 pm AST
5:00 pm MST
9:00 pm AST
6:00 pm MST
10:00 pm AST
7:00 pm MST
11:00 pm AST
8:00 pm MST

Scheduling between the two

Working hours overlap from 12:00 pm to 6:00 pm AST, which is 9:00 am to 3:00 pm MST. Anything inside that window falls in the normal working day at both ends.

A note on AST: it can also mean Arabia Standard Time (UTC+3). This page means Atlantic Time.

Atlantic Time (AST) is used in Nova Scotia, New Brunswick and Puerto Rico

Mountain Time (MST) is used in Salt Lake City, Albuquerque and Calgary. Arizona keeps MST all year and does not follow MDT.

Other conversions