AST to MST Converter
Convert Atlantic Standard Time (AST) to Mountain Standard Time (MST) in one step. Because mST is 3 hours behind AST, the math is a fixed 3 hours shift. Adjust the time or date and watch it update.
Daylight saving notes
In the United States and Canada, daylight saving time runs from the second Sunday in March to the first Sunday in November. That affects Atlantic Standard Time (AST).
AST to MST conversion chart
For example, a 9:00 AM AST meeting takes place at 6:00 AM MST. Concretely, when Halifax (AST) and Denver (MST) set up a call, mST is 3 hours behind AST.
| AST time | MST time |
|---|---|
| 12:00 AM | 9:00 PM−1 day |
| 1:00 AM | 10:00 PM−1 day |
| 2:00 AM | 11:00 PM−1 day |
| 3:00 AM | 12:00 AM |
| 4:00 AM | 1:00 AM |
| 5:00 AM | 2:00 AM |
| 6:00 AM | 3:00 AM |
| 7:00 AM | 4:00 AM |
| 8:00 AM | 5:00 AM |
| 9:00 AM | 6:00 AM |
| 10:00 AM | 7:00 AM |
| 11:00 AM | 8:00 AM |
| 12:00 PM | 9:00 AM |
| 1:00 PM | 10:00 AM |
| 2:00 PM | 11:00 AM |
| 3:00 PM | 12:00 PM |
| 4:00 PM | 1:00 PM |
| 5:00 PM | 2:00 PM |
| 6:00 PM | 3:00 PM |
| 7:00 PM | 4:00 PM |
| 8:00 PM | 5:00 PM |
| 9:00 PM | 6:00 PM |
| 10:00 PM | 7:00 PM |
| 11:00 PM | 8:00 PM |
This chart uses the fixed AST and MST offsets; the live converter above follows current daylight saving.
Convert AST to MST Time Zone
Everything you need for AST to MST — the difference, the current times, and how to plan around it.
Converting AST to MST, step by step
It takes three quick steps:
- Click the AST field on the left and pick the time you want to convert.
- The matching MST time updates on the right automatically — there’s no button to press.
- Need a different day? Click the date field and the result follows, rolling over if it crosses midnight.
AST vs MST: what's the time gap?
MST is 3 hours behind AST. In everyday terms, once you know the time on one side you just subtract 3 hours to get the other — so a call between Halifax and Denver is always 3 hours apart.
What's the current time in MST?
Right now the time in Mountain Standard Time (MST) is Monday, June 29, 2026 · 10:53:57 AM. It ticks every second, so you’re always looking at the live MST clock.
And what time is it in AST?
And in Atlantic Standard Time (AST), it’s currently Monday, June 29, 2026 · 1:53:57 PM. Compare the two and the 3 hours gap is easy to see.
What's the best time for a AST–MST call?
For example, a 9:00 AM AST meeting takes place at 6:00 AM MST. The trick is to aim for a slot that lands inside normal working hours on both sides. Once you’ve found a time, hit Share on the converter to copy a link with the time built in — easy to send to a colleague. Juggling three or more zones? The meeting planner highlights the hours that overlap for everyone.
Does daylight saving time change the AST–MST difference?
The labels AST and MST are fixed offsets, so the result on this page is always exact. Both regions move their clocks for daylight saving on roughly the same weekends, so the 3 hours gap usually holds steady right through the year.
How accurate is this AST to MST conversion?
We don’t guess. AST and MST times are worked out from the official IANA time zone database, the trusted standard that operating systems use worldwide. Because daylight-saving rules and regional offsets do change over time, we track those updates rather than relying on a fixed number — which is exactly where many converters slip up.
Convert AST to other time zones
- UTC Coordinated Universal Time
- GMT Greenwich Mean Time
- EST Eastern Standard Time
- EDT Eastern Daylight Time
- CST Central Standard Time
- CDT Central Daylight Time
- MST Mountain Standard Time
- MDT Mountain Daylight Time
- PST Pacific Standard Time
- PDT Pacific Daylight Time
- AKST Alaska Standard Time
- AKDT Alaska Daylight Time
- HST Hawaii Standard Time
- ADT Atlantic Daylight Time
- NST Newfoundland Standard Time
- NDT Newfoundland Daylight Time
- BRT Brasília Time
- ART Argentina Time
- WET Western European Time
- WEST Western European Summer Time
- CET Central European Time
- CEST Central European Summer Time
- EET Eastern European Time
- EEST Eastern European Summer Time
- BST British Summer Time
- IST Irish Standard Time
- MSK Moscow Standard Time
- TRT Turkey Time
- WAT West Africa Time
- CAT Central Africa Time
- EAT East Africa Time
- SAST South Africa Standard Time
- GST Gulf Standard Time
- IST Israel Standard Time
- IDT Israel Daylight Time
- IST India Standard Time
- PKT Pakistan Standard Time
- BDT Bangladesh Standard Time
- ICT Indochina Time
- WIB Western Indonesian Time
- WITA Central Indonesian Time
- WIT Eastern Indonesian Time
- CST China Standard Time
- HKT Hong Kong Time
- SGT Singapore Time
- PHT Philippine Time
- JST Japan Standard Time
- KST Korea Standard Time
- AWST Australian Western Standard Time
- ACST Australian Central Standard Time
- ACDT Australian Central Daylight Time
- AEST Australian Eastern Standard Time
- AEDT Australian Eastern Daylight Time
- NZST New Zealand Standard Time
- NZDT New Zealand Daylight Time
Convert to MST from other time zones
- UTC Coordinated Universal Time
- GMT Greenwich Mean Time
- EST Eastern Standard Time
- EDT Eastern Daylight Time
- CST Central Standard Time
- CDT Central Daylight Time
- MDT Mountain Daylight Time
- PST Pacific Standard Time
- PDT Pacific Daylight Time
- AKST Alaska Standard Time
- AKDT Alaska Daylight Time
- HST Hawaii Standard Time
- AST Atlantic Standard Time
- ADT Atlantic Daylight Time
- NST Newfoundland Standard Time
- NDT Newfoundland Daylight Time
- BRT Brasília Time
- ART Argentina Time
- WET Western European Time
- WEST Western European Summer Time
- CET Central European Time
- CEST Central European Summer Time
- EET Eastern European Time
- EEST Eastern European Summer Time
- BST British Summer Time
- IST Irish Standard Time
- MSK Moscow Standard Time
- TRT Turkey Time
- WAT West Africa Time
- CAT Central Africa Time
- EAT East Africa Time
- SAST South Africa Standard Time
- GST Gulf Standard Time
- IST Israel Standard Time
- IDT Israel Daylight Time
- IST India Standard Time
- PKT Pakistan Standard Time
- BDT Bangladesh Standard Time
- ICT Indochina Time
- WIB Western Indonesian Time
- WITA Central Indonesian Time
- WIT Eastern Indonesian Time
- CST China Standard Time
- HKT Hong Kong Time
- SGT Singapore Time
- PHT Philippine Time
- JST Japan Standard Time
- KST Korea Standard Time
- AWST Australian Western Standard Time
- ACST Australian Central Standard Time
- ACDT Australian Central Daylight Time
- AEST Australian Eastern Standard Time
- AEDT Australian Eastern Daylight Time
- NZST New Zealand Standard Time
- NZDT New Zealand Daylight Time
Frequently asked questions
How many hours behind AST is MST?
MST is 3 hours behind AST — a fixed 3 hours difference, since both are fixed-offset labels.
What time is it in MST when it's 12:00 PM AST?
When it's 12:00 PM (noon) AST, it's 9:00 AM MST.
Do AST or MST use daylight saving time?
Atlantic Standard Time (AST) observes daylight saving, alternating with ADT; Mountain Standard Time (MST) observes daylight saving, alternating with MDT.
Why might the real-world AST–MST difference change during the year?
The labels AST and MST are fixed offsets, so this converter is always exact. But Atlantic Standard Time's region switches between standard and summer time, so for part of the year you may actually want ADT to MST. Always check which label a region is currently using before you schedule.