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MDT to AST

+2h

MDT

MDTSOURCE
UTC-06:00☀ DST active
HH12
:
MM00
  
12:00 (24-hr)
12 AM6 AM12 PM6 PM12 AM

AST

AST
UTC-03:00☀ DST active
HH02
:
MM00
  
14:00 (24-hr)
12 AM6 AM12 PM6 PM12 AM
MDT
AST
12:00 AM
3:00 AM
2:00 AM
5:00 AM
4:00 AM
7:00 AM
6:00 AM
9:00 AM
8:00 AM
11:00 AM
10:00 AM
1:00 PM
12:00 PM
3:00 PM
2:00 PM
5:00 PM
4:00 PM
7:00 PM
6:00 PM
9:00 PM
8:00 PM
11:00 PM
10:00 PM
1:00 AM+1

Green rows indicate typical business hours (9 AM - 5 PM)

MDT and AST on the World Map

The map below highlights the MDT (Mountain Daylight Time) and AST (Atlantic Standard Time) timezone regions across the globe.

MDTASTDenverCalgaryEdmontonSalt Lake CityHalifaxSan JuanSanto DomingoCaracas
MDT Zone
→
AST Zone

Explore all world timezones interactively →

MDT – Mountain Daylight Time

UTC-06:00

Mountain Daylight Time (MDT) is the daylight saving offset in the Mountain Time Zone, 6 hours behind UTC.

Countries in MDT
United States (Mountain)Canada (Alberta)
Major Cities in MDT
DenverCalgaryEdmontonSalt Lake CityBoise
Key Facts about MDT
  • •MDT shares the same offset as CST (UTC-06:00).
  • •Arizona does not switch to MDT, remaining on MST.
Daylight Saving:Yes – switches to MST
Learn more about MDT on Wikipedia

AST – Atlantic Standard Time

UTC-04:00

Atlantic Standard Time (AST) is the time zone for the Canadian Atlantic provinces and the Caribbean, 4 hours behind UTC.

Countries in AST
Canada (Atlantic provinces)Puerto RicoUS Virgin IslandsDominican RepublicVenezuelaBoliviaBarbadosTrinidad and Tobago
Major Cities in AST
HalifaxSan JuanSanto DomingoCaracasLa PazFrederictonCharlottetown
Key Facts about AST
  • •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.
Daylight Saving:Yes – switches to ADT
Learn more about AST on Wikipedia

Comparing Time Zones: MDT and AST

MDT runs on Mountain Daylight Time (MDT) at UTC-06:00. AST runs on Atlantic Standard Time (AST) at UTC-04:00. That puts MDT 2 hours ahead of AST — a difference of +2h at the current offsets.

In practice, when it is 9:00 AM in MDT it is 11:00 AM in AST. Midnight in MDT is 2:00 AM in AST. Neither zone observes daylight saving time, so the offset between them stays constant all year.

MDT to AST time conversion table

MDT (MDT)AST (AST)Day
12:00 AM2:00 AMsame day
6:00 AM8:00 AMsame day
7:00 AM9:00 AMsame day
8:00 AM10:00 AMsame day
9:00 AM11:00 AMsame day
12:00 PM2:00 PMsame day
3:00 PM5:00 PMsame day
5:00 PM7:00 PMsame day
6:00 PM8:00 PMsame day
9:00 PM11:00 PMsame day

Why people convert MDT to AST time

  • Scheduling a call from MDT to AST: a 10:00 AM start in MDT lands at 12:00 PM in AST, so you can confirm the slot without doing the arithmetic yourself.
  • Finding shared working hours: both MDT and AST are inside the 9-to-5 working day between 9:00 AM and 3:00 PM MDT time (11:00 AM–5:00 PM AST). That is roughly 6 hours of usable overlap.
  • Booking travel or deliveries: tracking AST local time against MDT keeps pickup windows and arrival estimates honest across the +2h offset.
  • Always state the zone abbreviation, not just the hour. "3:00 PM MDT" is unambiguous; "3 PM" across a +2h gap is not.
  • Block 9:00 AM–3:00 PM MDT as the recurring meeting window if you work primarily from MDT and need AST colleagues present.

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.

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.

Best time to call between MDT and AST

Both MDT and AST sit inside the 9 AM – 5 PM working day between 9:00 AM–3:00 PM MDT, which is 11:00 AM–5:00 PM AST. That gives roughly 6 hours of shared time — the safest window for a live call or meeting.

Business hours overlap

MDT and AST share 6 hours of working-hours overlap (9:00 AM–3:00 PM MDT), so scheduling a live meeting is straightforward.

MDT is 2 hours ahead of AST (MDT UTC-06:00 → AST UTC-04:00). The shared working window is 9:00 AM–3:00 PM MDT. Remember to re-check around daylight-saving transitions.

🕐 Daylight Saving Time Info

MDT

☀ Currently in DST

Standard: UTC-07:00 · DST: UTC-06:00

Clocks fall back on Sun, Nov 1, 2026

AST

☀ Currently in DST

Standard: UTC-04:00 · DST: UTC-03:00

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:

⏳
History of Timekeeping
From sundials to atomic clocks - 5000 years of measuring time
🌍
How Time Zones Work
UTC, offsets, and why zones don't follow straight lines
☀️
Daylight Saving Time
DST dates, which countries observe it, and the ongoing debate

Frequently Asked Questions

What is the time difference between MDT and AST?

MDT (MDT, UTC-06:00) is 2 hours ahead of AST (AST, UTC-04:00). The gap is currently +2h.

How do I convert MDT time to AST time?

Add +2h to MDT local time. For example, 9:00 AM in MDT is 11:00 AM in AST.

What time is it in AST right now?

AST uses AST at UTC-04:00. Use the live converter at the top of this page — it updates in real time and already accounts for the +2h offset from MDT.

What is the best time to call AST from MDT?

Call between 9:00 AM and 3:00 PM MDT — that maps to 11:00 AM–5:00 PM AST and keeps both parties inside the working day.

Which is ahead, MDT or AST?

MDT is 2 hours ahead of AST. When it is 12:00 PM in MDT it is 2:00 PM in AST.

Does daylight saving time affect the MDT–AST difference?

Neither zone observes daylight saving time, so the +2h offset between MDT and AST is fixed all year.

Which other cities share MDT's time zone?

MDT also covers Denver, Calgary, Edmonton, Salt Lake City, Boise.

Which countries use MDT, MDT's zone?

MDT is used in United States (Mountain), Canada (Alberta).

Is there a day difference between MDT and AST?

Not normally. The +2h gap only pushes the date over for late-evening times.

What is the time difference between MDT and AST?

AST is +2h from MDT.

What timezone is MDT in?

MDT operates on its local timezone.

What timezone is AST in?

AST operates on its local timezone.

Which countries use MDT (Mountain Daylight Time)?

MDT is used in United States (Mountain), Canada (Alberta).

Does MDT observe daylight saving time?

Yes, MDT switches to MST during summer months.

What are some interesting facts about MDT?

MDT shares the same offset as CST (UTC-06:00). Arizona does not switch to MDT, remaining on MST.

Which cities are in the AST timezone?

Major cities in the AST timezone include Halifax, San Juan, Santo Domingo, Caracas, La Paz, Fredericton, Charlottetown.

What is the UTC offset for AST?

Atlantic Standard Time (AST) is at UTC-04:00. During daylight saving time, it shifts to ADT.

What should I know about the AST timezone?

Puerto Rico uses AST year-round and does not observe DST. AST is 1 hour ahead of EST.

When is it midnight in MDT, what time is it in AST?

When it is 12:00 AM (midnight) in MDT (MDT), it is +2h later in AST (AST).

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Related Timezone Conversions

mdt→denvermdt→mstmdt→new yorkmdt→londonast→halifaxast→new yorkast→londonast→dubai

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