AST to MDT
-2hAST
ASTSOURCEMDT
MDTGreen rows indicate typical business hours (9 AM - 5 PM)
AST and MDT on the World Map
The map below highlights the AST (Atlantic Standard Time) and MDT (Mountain Daylight Time) timezone regions across the globe.
AST – Atlantic Standard Time
UTC-04:00Atlantic Standard Time (AST) is the time zone for the Canadian Atlantic provinces and the Caribbean, 4 hours behind UTC.
- •Puerto Rico uses AST year-round and does not observe DST.
- •AST is 1 hour ahead of EST.
- •Halifax, the capital of Nova Scotia, is the largest city in AST Canada.
MDT – Mountain Daylight Time
UTC-06:00Mountain Daylight Time (MDT) is the daylight saving offset in the Mountain Time Zone, 6 hours behind UTC.
- •MDT shares the same offset as CST (UTC-06:00).
- •Arizona does not switch to MDT, remaining on MST.
AST to MDT Time Difference – Complete Guide
AST runs on Atlantic Standard Time (AST) at UTC-04:00. MDT runs on Mountain Daylight Time (MDT) at UTC-06:00. That puts AST 2 hours behind MDT — a difference of -2h at the current offsets.
In practice, when it is 9:00 AM in AST it is 7:00 AM in MDT. Midnight in AST is 10:00 PM in MDT. Neither zone observes daylight saving time, so the offset between them stays constant all year.
AST to MDT time conversion table
| AST (AST) | MDT (MDT) | Day |
|---|---|---|
| 12:00 AM | 10:00 PM | previous day |
| 6:00 AM | 4:00 AM | same day |
| 7:00 AM | 5:00 AM | same day |
| 8:00 AM | 6:00 AM | same day |
| 9:00 AM | 7:00 AM | same day |
| 12:00 PM | 10:00 AM | same day |
| 3:00 PM | 1:00 PM | same day |
| 5:00 PM | 3:00 PM | same day |
| 6:00 PM | 4:00 PM | same day |
| 9:00 PM | 7:00 PM | same day |
Why people convert AST to MDT time
- Scheduling a call from AST to MDT: a 10:00 AM start in AST lands at 8:00 AM in MDT, so you can confirm the slot without doing the arithmetic yourself.
- Finding shared working hours: both AST and MDT are inside the 9-to-5 working day between 11:00 AM and 5:00 PM AST time (9:00 AM–3:00 PM MDT). That is roughly 6 hours of usable overlap.
- Watching a live event or market open: AST viewers need 7:00 AM in MDT to catch a 9:00 AM start there, and 2:00 AM if the event is anchored to AST.
- Always state the zone abbreviation, not just the hour. "3:00 PM AST" is unambiguous; "3 PM" across a -2h gap is not.
- Block 11:00 AM–5:00 PM AST as the recurring meeting window if you work primarily from AST and need MDT colleagues present.
About AST (Atlantic Standard Time)
Atlantic Standard Time (AST) covers Canada's Atlantic provinces (Nova Scotia, New Brunswick, Prince Edward Island, and most of Labrador), as well as several Caribbean nations. Puerto Rico and the US Virgin Islands use AST year-round without daylight saving time. The Canadian provinces switch to Atlantic Daylight Time (ADT) in summer.
About MDT (Mountain Daylight Time)
Mountain Daylight Time (MDT) is observed during summer months in the Mountain Time Zone, except in Arizona which stays on MST year-round. MDT aligns with Central Standard Time (CST) at UTC-06:00.
Best time to call between AST and MDT
Both AST and MDT sit inside the 9 AM – 5 PM working day between 11:00 AM–5:00 PM AST, which is 9:00 AM–3:00 PM MDT. That gives roughly 6 hours of shared time — the safest window for a live call or meeting.
Business hours overlap
AST and MDT share 6 hours of working-hours overlap (11:00 AM–5:00 PM AST), so scheduling a live meeting is straightforward.
AST is 2 hours behind MDT (AST UTC-04:00 → MDT UTC-06:00). The shared working window is 11:00 AM–5:00 PM AST. Remember to re-check around daylight-saving transitions.
🕐 Daylight Saving Time Info
AST
☀ Currently in DST
Standard: UTC-04:00 · DST: UTC-03:00
Clocks fall back on Sun, Nov 1, 2026
MDT
☀ Currently in DST
Standard: UTC-07:00 · DST: UTC-06:00
Clocks fall back on Sun, Nov 1, 2026
Learn More About Time
Dive deeper into the fascinating world of timekeeping, time zones, and how they shape our global society:
Frequently Asked Questions
What is the time difference between AST and MDT?
AST (AST, UTC-04:00) is 2 hours behind MDT (MDT, UTC-06:00). The gap is currently -2h.
How do I convert AST time to MDT time?
Add -2h to AST local time. For example, 9:00 AM in AST is 7:00 AM in MDT.
What time is it in MDT right now?
MDT uses MDT at UTC-06:00. Use the live converter at the top of this page — it updates in real time and already accounts for the -2h offset from AST.
What is the best time to call MDT from AST?
Call between 11:00 AM and 5:00 PM AST — that maps to 9:00 AM–3:00 PM MDT and keeps both parties inside the working day.
Which is behind, AST or MDT?
AST is 2 hours behind MDT. When it is 12:00 PM in AST it is 10:00 AM in MDT.
Does daylight saving time affect the AST–MDT difference?
Neither zone observes daylight saving time, so the -2h offset between AST and MDT is fixed all year.
Which other cities share AST's time zone?
AST also covers Halifax, San Juan, Santo Domingo, Caracas, La Paz, Fredericton, Charlottetown.
Which countries use AST, AST's zone?
AST is used in Canada (Atlantic provinces), Puerto Rico, US Virgin Islands, Dominican Republic, Venezuela, Bolivia, Barbados, Trinidad and Tobago.
Is there a day difference between AST and MDT?
Not normally. The -2h gap only pushes the date over the previous day.
What is the time difference between AST and MDT?
MDT is -2h from AST.
What timezone is AST in?
AST operates on its local timezone.
What timezone is MDT in?
MDT operates on its local timezone.
Which countries use AST (Atlantic Standard Time)?
AST is used in Canada (Atlantic provinces), Puerto Rico, US Virgin Islands, Dominican Republic, Venezuela, Bolivia, and 2 more countries.
Does AST observe daylight saving time?
Yes, AST switches to ADT during summer months.
What are some interesting facts about AST?
Puerto Rico uses AST year-round and does not observe DST. AST is 1 hour ahead of EST.
Which cities are in the MDT timezone?
Major cities in the MDT timezone include Denver, Calgary, Edmonton, Salt Lake City, Boise.
What is the UTC offset for MDT?
Mountain Daylight Time (MDT) is at UTC-06:00. During daylight saving time, it shifts to MST.
What should I know about the MDT timezone?
MDT shares the same offset as CST (UTC-06:00). Arizona does not switch to MDT, remaining on MST.
When is it midnight in AST, what time is it in MDT?
When it is 12:00 AM (midnight) in AST (AST), it is -2h later in MDT (MDT).
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See every conversion from AST →·See every conversion from MDT →