MDT to AST Converter & Meeting Planner
Quick answer: 9:00 AM MDT = 11:00 AM AST (fixed -06:00 standard offset — not DST-adjusted). Use the interactive converter below for DST-aware local-time scheduling.
Planning a call or meeting between Mountain Daylight Time (MDT) and Atlantic Standard Time (AST)? You need to account for the standard time difference. Atlantic Standard Time is normally 2 hours ahead of Mountain Daylight Time. Whether you are coordinating between teams in Denver and Salt Lake City and Halifax and San Juan, our live tool has you covered. Use our interactive overlap studio below to find the perfect waking hours for both regions, taking into account any seasonal Daylight Saving Time (DST) changes.
24-Hour Conversion Table
Quick reference: 12:00 AM MDT = 2:00 AM AST. The full 24-hour MDT to AST table below uses fixed standard offsets for exact abbreviation searches.
Example: 3:00 PM MDT = 5:00 PM AST.
| MDT Time | AST Time |
|---|---|
| 12:00 AM (00:00) | 2:00 AM (02:00) |
| 1:00 AM (01:00) | 3:00 AM (03:00) |
| 2:00 AM (02:00) | 4:00 AM (04:00) |
| 3:00 AM (03:00) | 5:00 AM (05:00) |
| 4:00 AM (04:00) | 6:00 AM (06:00) |
| 5:00 AM (05:00) | 7:00 AM (07:00) |
| 6:00 AM (06:00) | 8:00 AM (08:00) |
| 7:00 AM (07:00) | 9:00 AM (09:00) |
| 8:00 AM (08:00) | 10:00 AM (10:00) |
| 9:00 AM (09:00) | 11:00 AM (11:00) |
| 10:00 AM (10:00) | 12:00 PM (12:00) |
| 11:00 AM (11:00) | 1:00 PM (13:00) |
| 12:00 PM (12:00) | 2:00 PM (14:00) |
| 1:00 PM (13:00) | 3:00 PM (15:00) |
| 2:00 PM (14:00) | 4:00 PM (16:00) |
| 3:00 PM (15:00) | 5:00 PM (17:00) |
| 4:00 PM (16:00) | 6:00 PM (18:00) |
| 5:00 PM (17:00) | 7:00 PM (19:00) |
| 6:00 PM (18:00) | 8:00 PM (20:00) |
| 7:00 PM (19:00) | 9:00 PM (21:00) |
| 8:00 PM (20:00) | 10:00 PM (22:00) |
| 9:00 PM (21:00) | 11:00 PM (23:00) |
| 10:00 PM (22:00) | 12:00 AM (00:00)+1 day |
| 11:00 PM (23:00) | 1:00 AM (01:00)+1 day |
Best time to call Halifax from Denver
For most work calls, compare the normal business day in Denver (MDT) with the business day in Halifax (AST). MDT commonly covers North America, while AST is mainly associated with North America, Caribbean.
⚠️ Note: 2026-07-05 is not a normal workday in one or both regions based on their configured calendar. The overlap below should be treated as a reference, not a guaranteed office-hours window.
✅ The most practical overlap on 2026-07-05 is usually 9:00 AM - 2:00 PM MDT, which corresponds to 12:00 PM - 5:00 PM AST. This window sits inside the typical MDT workday (9:00 AM - 5:00 PM) and the AST workday (9:00 AM - 5:00 PM).
- DST Safety: MDT or AST may shift during Daylight Saving Time. Always confirm the converted time for your specific date.
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Frequently Asked Questions
What is the time difference between MDT and AST?
During standard time, Atlantic Standard Time is 2 hours ahead of Mountain Daylight Time.
When does MDT start and end?
MDT begins on the second Sunday in March at 02:00 local MST time, when clocks spring forward one hour from MST (UTC-7) to MDT (UTC-6). It ends on the first Sunday in November at 02:00 local MDT time, when clocks fall back to MST. In 2026, MDT runs from March 8 through November 1, covering the majority of the calendar year.
Is Arizona on MDT?
Most of Arizona — including Phoenix and Tucson — does not observe Daylight Saving Time and remains on MST (UTC-7) year-round under a state law in effect since 1968, meaning Arizona does not advance to MDT each March. The significant exception is the Navajo Nation, a sovereign territory spanning parts of northeastern Arizona, southeastern Utah, and northwestern New Mexico, which does observe DST and shifts to MDT on the standard federal schedule.
Does the Caribbean observe Daylight Saving Time?
The vast majority of Caribbean nations and territories — including Puerto Rico, the Dominican Republic, the US Virgin Islands, Trinidad and Tobago, and Barbados — do not observe Daylight Saving Time and remain on AST (UTC-4) year-round. This means these territories share the same clock as Halifax only during the Atlantic Standard Time window in winter, diverging by one hour once Canada and Bermuda advance to ADT each spring.
What is the difference between AST and ADT?
AST (Atlantic Standard Time) is the standard winter offset at UTC-4:00, observed from the first Sunday in November through the second Sunday in March across all AST regions. ADT (Atlantic Daylight Time) is the summer offset at UTC-3:00, applied by Eastern Canadian provinces and Bermuda when they advance their clocks by one hour during Daylight Saving Time.