World Timezones

GMT to AST-ATLANTIC Converter

Compare AST-ATLANTIC to GMT instead
Greenwich Mean Time5:35 amFri, Jun 5
Greenwich Mean TimeBST
Europe · UTC+1
5:35 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
Atlantic TimeADT
North America · UTC-3
1:35 amFri, Jun 5
8p
9p
10p
11p
12a
1a
2a
3a
4a
5a
6a
7a
8a
9a
10a
11a
12p
1p
2p
3p
4p
5p
6p
7p

Offset

The time difference between Greenwich Mean Time and Atlantic Time is 4 hours.

4 hours

Greenwich Mean Time (BST) is ahead of Atlantic Time (ADT).

BST: UTC+1

ADT: UTC-3

Both zones are currently observing daylight saving time.

When to schedule

Business-hours overlap: 1 PM–5 PM in Greenwich Mean Time (9 AM–1 PM in Atlantic Time).

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

Suggested time: 3:00 PM Greenwich Mean Time (11:00 AM Atlantic 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.

United Kingdom

  • Good FridayFri, Apr 3
  • Early May Bank HolidayMon, May 4
  • Spring Bank HolidayMon, May 25
  • Christmas DayFri, Dec 25
  • St. Stephen's DayMon, Dec 28

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

About these zones

Greenwich Mean Time is also known as GMT, or BST. To call United Kingdom, dial +44.

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

Atlantic Time is approximately 2,850 miles west of Greenwich Mean Time.

Quick reference

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

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

Daylight saving time

Both zones observe daylight saving time, but they transition on different dates.

Greenwich Mean Time: next transition on Sunday, October 25, 2026.

Atlantic Time: next transition on Sunday, November 1, 2026.

For approximately 7 days between transitions, the offset between Greenwich Mean Time and Atlantic Time differs from its typical value. Recurring meetings during this window will shift by one hour.

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

Daylight today

Greenwich Mean Time
Sunrise
4:47 AM
Sunset
9:13 PM
Day length
16h 25m
Atlantic Time
Sunrise
5:31 AM
Sunset
8:56 PM
Day length
15h 25m

Daylight overlap: 11h 41m — 9:31 AM–9:13 PM in Greenwich Mean Time (5:31 AM–5:13 PM in Atlantic Time). Both locations are in daylight during this window.

Cities in these zones

Cities in Atlantic Time

Browse all cities to see the current local time anywhere.

Airports in these zones

Airports in Greenwich Mean Time

  • LCY
  • LGW
  • LHR
  • LTN
  • STN
  • BHX
  • EMA
  • GLA
  • PIK
  • LBA

Airports in Atlantic Time

  • YHZ

Related conversions

Common conversions

What is 9:00 am GMT in AST-ATLANTIC?
9:00 am GMT is 5:00 am AST-ATLANTIC.
What is 12:00 pm GMT in AST-ATLANTIC?
12:00 pm GMT is 8:00 am AST-ATLANTIC.
What is 12:30 pm GMT in AST-ATLANTIC?
12:30 pm GMT is 8:30 am AST-ATLANTIC.
What is 2:00 pm GMT in AST-ATLANTIC?
2:00 pm GMT is 10:00 am AST-ATLANTIC.
What is 5:00 pm GMT in AST-ATLANTIC?
5:00 pm GMT is 1:00 pm AST-ATLANTIC.
What is 11:30 pm GMT in AST-ATLANTIC?
11:30 pm GMT is 7:30 pm AST-ATLANTIC.