MST to AST Converter
Convert time between Mountain Standard Time (MST) and Atlantic Standard Time (AST)
Mountain Standard Time (MST)
Atlantic Standard Time (AST)
Time Difference
Atlantic Standard Time (AST) is 0 hours ahead of Mountain Standard Time (MST)
Select Date
Select Time
Quick Reference
| MST | AST |
|---|---|
| 19:00 | 22:00 |
| 21:00 | 00:00 |
| 23:00 | 02:00 |
| 01:00 | 04:00 |
| 03:00 | 06:00 |
| 05:00 | 08:00 |
| 07:00 | 10:00 |
| 09:00 | 12:00 |
| 11:00 | 14:00 |
| 13:00 | 16:00 |
| 15:00 | 18:00 |
| 17:00 | 20:00 |
Top 10 Most Common Time Zones
| Abbreviation | Full Name | UTC Offset | Typical Use |
|---|---|---|---|
| UTC | Coordinated Universal Time | UTC ±0 | Global reference standard (servers, logs, APIs) |
| EST / EDT | Eastern (US) Time | UTC −5 / −4 | New York, Toronto — North American business hub |
| CST / CDT | Central (US) Time | UTC −6 / −5 | Chicago, Dallas — US central business region |
| PST / PDT | Pacific (US) Time | UTC −8 / −7 | San Francisco, Los Angeles — tech industry standard |
| GMT / BST | Greenwich Mean / British Summer Time | UTC 0 / +1 | UK, used globally as a reference with UTC |
| CET / CEST | Central European (Summer) Time | UTC +1 / +2 | Paris, Berlin, Amsterdam — EU business core |
| IST | India Standard Time | UTC +5:30 | India — major IT & outsourcing region |
| CST | China Standard Time | UTC +8 | Beijing, Shanghai — East Asia business hub |
| JST | Japan Standard Time | UTC +9 | Tokyo — finance & tech hub |
| AEST / AEDT | Australian Eastern (Daylight) Time | UTC +10 / +11 | Sydney, Melbourne — APAC regional business |
Why Time Zone Abbreviations Are Ambiguous
Unlike standardized identifiers (like America/New_York or Europe/London from the IANA tz database), abbreviations such as "CST" or "IST" are not globally unique. They can refer to different time zones depending on context — country, region, or even time of year (due to daylight saving time).
Common Ambiguous Time Zone Abbreviations
| Abbrev. | Common Meaning(s) | UTC Offset | Region(s) |
|---|---|---|---|
| CST | Central Standard Time / China Standard Time / Cuba Standard Time | UTC−6 / UTC+8 / UTC−5 | North America, China, Cuba |
| IST | Indian Standard Time / Irish Standard Time / Israel Standard Time | UTC+5:30 / UTC+1 / UTC+2 | India, Ireland, Israel |
| AST | Atlantic Standard Time / Arabia Standard Time | UTC−4 / UTC+3 | Caribbean, Canada, Middle East |
| PST | Pacific Standard Time / Philippine Standard Time | UTC−8 / UTC+8 | North America, Philippines |
| EST | Eastern Standard Time (North America / Australia) | UTC−5 / UTC+10 | North America, Australia |
✅ Best Practice
To avoid ambiguity, always:
- Use IANA tz identifiers — e.g.,
America/New_Yorkinstead of "EST" - Specify UTC offset explicitly — e.g.,
UTC−5when abbreviations must be used - Include the full timezone name — e.g., "Eastern Standard Time (EST)" with UTC offset
Related Time Zone Conversions
About MST to AST Time Conversion
Converting time between Mountain Standard Time (MST) and Atlantic Standard Time (AST) is essential for coordinating activities across Canada's western Mountain region and eastern Atlantic provinces. MST is UTC-7 during winter and UTC-6 during summer (MDT), while AST is UTC-4 during winter and UTC-3 during summer (ADT). The time difference remains constant at 3 hours throughout the year because both regions transition on the same dates.
This conversion is particularly useful for Canadian business operations spanning from Alberta and British Columbia to the Maritime provinces (Nova Scotia, New Brunswick, Prince Edward Island, and Newfoundland). Our converter uses the IANA timezone database to ensure accurate calculations while handling the complexities of seasonal timezone changes.
Common Use Cases for MST to AST Conversion
Business & Work
- Coordinating business operations across Canadian provinces from Mountain to Atlantic regions
- Scheduling meetings and conference calls between Western and Eastern Canada
- Planning project timelines that span different Canadian time zones
Personal & Travel
- Planning travel between Western and Eastern Canadian regions
- Coordinating with family and friends across Canadian provinces
- Managing events and activities across regional time boundaries
Time Zone Information
Mountain Standard Time (MST)
- UTC Offset: UTC-7 (UTC-6 during MDT)
- IANA Timezone: America/Denver
- Daylight Saving: MST: November to March, MDT: March to November
- Major Cities: Denver, Calgary, Edmonton, Salt Lake City, Boise
- Coverage: Mountain region of western North America including Alberta, British Columbia, and western United States
Atlantic Standard Time (AST)
- UTC Offset: UTC-4 (UTC-3 during ADT)
- IANA Timezone: America/Halifax
- Daylight Saving: AST: November to March, ADT: March to November
- Major Cities: Halifax, Saint John, St. John's, Fredericton, Moncton
- Coverage: Atlantic Canada including Nova Scotia, New Brunswick, Prince Edward Island, and Newfoundland
Quick Reference: MST to AST
Remember: AST is always 3 hours ahead of MST. The time difference remains consistent year-round because both regions transition to daylight saving time on the same dates (second Sunday in March and first Sunday in November).
Frequently Asked Questions
What is the time difference between MST and AST?
Mountain Standard Time (MST) is UTC-7, while Atlantic Standard Time (AST) is UTC-4. This means AST is 3 hours ahead of MST. When it's 12:00 PM in Denver during winter (MST), it would be 3:00 PM in Halifax during winter (AST). Notably, the 3-hour difference remains constant year-round because both regions transition to daylight saving time on the same dates.
When are MST and AST active?
Mountain Standard Time (MST) is active from the first Sunday in November to the second Sunday in March, while Atlantic Standard Time (AST) is active during the same period. Both regions observe daylight saving time from the second Sunday in March to the first Sunday in November, transitioning to MDT and ADT respectively. Because they transition on the same dates, the 3-hour difference is maintained year-round.
What regions use MST and AST?
MST covers the Mountain region including Colorado, Wyoming, Montana, Utah, New Mexico, Alberta, and British Columbia. Major cities include Denver, Calgary, and Edmonton. AST covers the Atlantic provinces of Canada including Nova Scotia, New Brunswick, Prince Edward Island, and Newfoundland. Major cities include Halifax, Saint John, St. John's, and Moncton. This conversion is primarily relevant for Canadian business coordination across western and eastern provinces.
Why is MST to AST conversion useful?
This conversion is essential for coordinating business operations across Canada, spanning from the Mountain provinces (Alberta, British Columbia) to the Atlantic provinces (Nova Scotia, New Brunswick, PEI, Newfoundland). Companies with offices or operations in both regions need this conversion for scheduling meetings, managing projects, and coordinating communications. The Canadian market spans these time zones significantly.
How do daylight saving transitions affect MST to AST scheduling?
One of the unique advantages of MST to AST conversion is that both regions transition to daylight saving time on the same dates: the second Sunday in March (to MDT and ADT respectively) and the first Sunday in November (back to MST and AST). This means the 3-hour time difference remains constant throughout the year, making scheduling more consistent. However, you should still specify the IANA timezone (America/Denver and America/Halifax) in calendar applications to ensure accuracy.
What makes this conversion different from US-only conversions?
Unlike conversions between US time zones, MST to AST involves cross-border Canadian coordination. The Atlantic region encompasses Newfoundland, which has its own timezone (NST/NDT, UTC-3.5/-2.5), but the Halifax-based AST/ADT is the primary timezone for most Atlantic Canada. This conversion is vital for Pan-Canadian business operations and reflects the geographic and economic importance of both the western energy sector and eastern maritime regions.
Pro Tips
- • AST is always 3 hours ahead of MST - a simple rule: add 3 hours to MST to get AST time.
- • The time difference between MST and AST remains constant at 3 hours year-round, unlike some other timezone pairs, because both regions observe daylight saving time on the same schedule.
- • Both MST and AST regions observe daylight saving time from the second Sunday in March to the first Sunday in November. During these periods, they transition to MDT (UTC-6) and ADT (UTC-3) respectively, maintaining the 3-hour difference.
- • When scheduling recurring meetings between Mountain and Atlantic regions, use your calendar application's IANA timezone settings (America/Denver and America/Halifax) to automatically handle daylight saving transitions.
- • Note that Newfoundland (St. John's) operates on its own timezone (NST/NDT, UTC-3.5/-2.5), which is only 30 minutes behind AST/ADT. This is important when coordinating with that province specifically.
- • The Atlantic provinces and Mountain regions have significant business ties through energy, technology, and maritime industries. Understanding this time conversion is essential for Pan-Canadian business coordination.
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