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DateAlmanac

What is MST in AST?

Atlantic Time is 3 hours ahead

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

Convert a time

AST — Atlantic Time

4:00 am

AST, Sat

Time in Denver
1:28:57 AM
Time in Halifax
4:28:57 AM
Difference
+3 h
Next clock change
March 14, 2027

Daylight saving

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.

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.

MST to AST conversion table

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

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

Scheduling between the two

Working hours overlap from 9:00 am to 3:00 pm MST, which is 12:00 pm to 6:00 pm AST. 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.

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

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

Other conversions