AST to MST Converter
MST is 3 hours behind AST. 9:00 AM AST = 6:00 AM MST.
MST is 3 hours behind AST. To convert AST to MST, subtract 3 hours from the AST time: 9:00 AM AST = 6:00 AM MST.
AST (Atlantic Time) is used in Nova Scotia, New Brunswick, PEI; Puerto Rico and the Eastern Caribbean (all year). MST (Mountain Time) is used in Denver, Salt Lake City, Albuquerque, Calgary, Edmonton; Phoenix (Arizona) all year.
AST here is Atlantic Standard Time, not Arabia Standard Time. Most of Arizona uses MST all year and does not switch to MDT.
AST to MST time conversion table
AST to MST on 6 Nov 2026. Today's date. Highlighted rows are 9 AM–5 PM in both places.
| AST | MST | Day |
|---|---|---|
| 12:00 AM AST | 9:00 PM MST | previous day |
| 1:00 AM AST | 10:00 PM MST | previous day |
| 2:00 AM AST | 11:00 PM MST | previous day |
| 3:00 AM AST | 12:00 AM MST | night |
| 4:00 AM AST | 1:00 AM MST | night |
| 5:00 AM AST | 2:00 AM MST | night |
| 6:00 AM AST | 3:00 AM MST | night |
| 7:00 AM AST | 4:00 AM MST | night |
| 8:00 AM AST | 5:00 AM MST | night |
| 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 | work hours |
| 1:00 PM AST | 10:00 AM MST | work hours |
| 2:00 PM AST | 11:00 AM MST | work hours |
| 3:00 PM AST | 12:00 PM MST | work hours |
| 4:00 PM AST | 1:00 PM MST | work hours |
| 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 | — |
- Work rows — 9 AM–5 PM in both places
- Night in the destination (10 PM–6 AM)
How to convert AST to MST
Subtract 3 hours from the AST time to get MST.
Example: 9:00 AM AST = 6:00 AM MST.
Across midnight: 1:00 AM AST = 10:00 PM MST (previous day). The date changes, so always check the day as well as the hour.
Time difference between AST and MST
The time difference between AST and MST is 3 hours all year – MST is behind AST.
AST and MST during daylight saving time
- AST next changes on 14 Mar 2027: clocks go forward one hour at 01:59 local time, from AST (UTC−4) to ADT (UTC−3).
- MST next changes on 14 Mar 2027: clocks go forward one hour at 01:59 local time, from MST (UTC−7) to MDT (UTC−6).
Best time for a meeting between AST and MST
AST and MST share 5 hours of the 9 AM–5 PM working day. Any time between 12:00 PM and 5:00 PM AST lands between 9:00 AM and 2:00 PM MST, inside working hours for both.
AST to MST FAQ
What is the time difference between AST and MST?
MST is 3 hours behind AST all year. 9:00 AM AST = 6:00 AM MST.
What is 9 AM AST in MST?
9:00 AM AST is 6:00 AM MST.
What is 12 PM (noon) AST in MST?
12:00 PM AST is 9:00 AM MST.
Is MST ahead of or behind AST?
MST is 3 hours behind AST, so it is earlier in MST than in AST.
Does AST change for daylight saving time?
Yes. AST next changes on 14 Mar 2027, when clocks go forward one hour from AST to ADT.
Does MST change for daylight saving time?
Yes. MST next changes on 14 Mar 2027, when clocks go forward one hour from MST to MDT.
What is the best time for a meeting between AST and MST?
AST and MST share 5 hours of the 9 AM–5 PM working day. Any time between 12:00 PM and 5:00 PM AST lands between 9:00 AM and 2:00 PM MST, inside working hours for both.
Is MT the same as MST?
MST is the winter (standard) name of Mountain Time (MT). From March to November the same clocks are called MDT. This converter always uses the one in force on the date you choose.
Related conversions
Convert MST to AST
Convert AST to other time zones
Convert other time zones to MST
Learn more
Updated 6 November 2026. Time zone data: IANA tz database.