World Timezones

AST-ATLANTIC to MST Converter

Compare MST to AST-ATLANTIC instead
Atlantic Time1:35 amFri, Jun 5
Atlantic TimeADT
North America · UTC-3
1:35 amFri, Jun 5
12a
1a
2a
3a
4a
5a
6a
7a
8a
9a
10a
11a
12p
1p
2p
3p
4p
5p
6p
7p
8p
9p
10p
11p
Mountain TimeMDT
North America · UTC-6
10:35 pmThu, Jun 4
9p
10p
11p
12a
1a
2a
3a
4a
5a
6a
7a
8a
9a
10a
11a
12p
1p
2p
3p
4p
5p
6p
7p
8p

Offset

The time difference between Atlantic Time and Mountain Time is 3 hours.

3 hours

Atlantic Time (ADT) is ahead of Mountain Time (MDT).

ADT: UTC-3

MDT: UTC-6

Both zones are currently observing daylight saving time.

When to schedule

Business-hours overlap: 12 PM–5 PM in Atlantic Time (9 AM–2 PM in Mountain Time).

Both teams are in working hours during this window on weekdays.

Suggested time: 2:00 PM Atlantic Time (11:00 AM Mountain Time).

This window may shift by an hour during daylight saving time.

Public holidays in 2026

National public holidays can affect availability — a counterpart is likely off work on their own holidays, so it's worth planning meetings and deadlines around them.

Canada

  • New Year's DayThu, Jan 1
  • Good FridayFri, Apr 3
  • Victoria DayMon, May 18
  • Canada DayWed, Jul 1
  • Labour DayMon, Sep 7
  • National Day for Truth and ReconciliationWed, Sep 30
  • ThanksgivingMon, Oct 12
  • Christmas DayFri, Dec 25

United States

  • New Year's DayThu, Jan 1
  • Martin Luther King, Jr. DayMon, Jan 19
  • Presidents DayMon, Feb 16
  • Memorial DayMon, May 25
  • Juneteenth National Independence DayFri, Jun 19
  • Independence DayFri, Jul 3
  • Labour DayMon, Sep 7
  • Columbus DayMon, Oct 12
  • Veterans DayWed, Nov 11
  • Thanksgiving DayThu, Nov 26
  • Christmas DayFri, Dec 25

About these zones

Atlantic Time is also known as AST, or ADT. To call Canada, dial +1.

Mountain Time is also known as MST, or MDT. To call United States, dial +1.

Mountain Time is approximately 2,100 miles west of Atlantic Time.

Quick reference

Full 24-hour conversion table — tap any time to open it in the converter.

AST-ATLANTICMSTDay
12:00 am9:00 pm-1 day
1:00 am10:00 pm-1 day
2:00 am11:00 pm-1 day
3:00 am12:00 amSame day
4:00 am1:00 amSame day
5:00 am2:00 amSame day
6:00 am3:00 amSame day
7:00 am4:00 amSame day
8:00 am5:00 amSame day
9:00 am6:00 amSame day
10:00 am7:00 amSame day
11:00 am8:00 amSame day
12:00 pm9:00 amSame day
1:00 pm10:00 amSame day
2:00 pm11:00 amSame day
3:00 pm12:00 pmSame day
4:00 pm1:00 pmSame day
5:00 pm2:00 pmSame day
6:00 pm3:00 pmSame day
7:00 pm4:00 pmSame day
8:00 pm5:00 pmSame day
9:00 pm6:00 pmSame day
10:00 pm7:00 pmSame day
11:00 pm8:00 pmSame day

Daylight saving time

Both Atlantic Time and Mountain Time observe daylight saving time and transition on the same date.

Next transition: Sunday, November 1, 2026 (fall back).

Because they transition simultaneously, the offset between these zones remains constant year-round.

See the daylight saving time page for transition dates across every time zone.

Daylight today

Atlantic Time
Sunrise
5:31 AM
Sunset
8:56 PM
Day length
15h 25m
Mountain Time
Sunrise
5:34 AM
Sunset
8:25 PM
Day length
14h 51m

Cities in these zones

Cities in Atlantic Time

Cities in Mountain Time

Browse all cities to see the current local time anywhere.

Airports in these zones

Airports in Atlantic Time

  • YHZ

Airports in Mountain Time

  • BJC
  • DEN
  • OGD
  • SLC

Related conversions

Common conversions

What is 9:00 am AST-ATLANTIC in MST?
9:00 am AST-ATLANTIC is 6:00 am MST.
What is 12:00 pm AST-ATLANTIC in MST?
12:00 pm AST-ATLANTIC is 9:00 am MST.
What is 12:30 pm AST-ATLANTIC in MST?
12:30 pm AST-ATLANTIC is 9:30 am MST.
What is 2:00 pm AST-ATLANTIC in MST?
2:00 pm AST-ATLANTIC is 11:00 am MST.
What is 5:00 pm AST-ATLANTIC in MST?
5:00 pm AST-ATLANTIC is 2:00 pm MST.
What is 11:30 pm AST-ATLANTIC in MST?
11:30 pm AST-ATLANTIC is 8:30 pm MST.