GMT to AST
On Oct 23, 2026, Atlantic Time is 4 hours behind UK time: 9:00 AM BST is 5:00 AM ADT. The gap changes during the year because of daylight saving time; the dates are below.
AST vs GMT over the next 12 months
| Period | AST is | Example |
|---|---|---|
| Oct 23, 2026 to Oct 25, 2026 | 4 hours behind | 9:00 AM BST = 5:00 AM ADT |
| Oct 25, 2026 to Nov 1, 2026 | 3 hours behind | 9:00 AM GMT = 6:00 AM ADT |
| Nov 1, 2026 to Mar 14, 2027 | 4 hours behind | 9:00 AM GMT = 5:00 AM AST |
| Mar 14, 2027 to Mar 28, 2027 | 3 hours behind | 9:00 AM GMT = 6:00 AM ADT |
| Mar 28, 2027 onwards | 4 hours behind | 9:00 AM BST = 5:00 AM ADT |
GMT to AST conversion table
Every hour of a weekday around Oct 23, 2026, in both zones.
| UK time | Atlantic Time |
|---|---|
| 12:00 AM | 9:00 PM (previous day) |
| 1:00 AM | 10:00 PM (previous day) |
| 2:00 AM | 11:00 PM (previous day) |
| 3:00 AM | 12:00 AM |
| 4:00 AM | 1:00 AM |
| 5:00 AM | 2:00 AM |
| 6:00 AM | 3:00 AM |
| 7:00 AM | 4:00 AM |
| 8:00 AM | 5:00 AM |
| 9:00 AM | 6:00 AM |
| 10:00 AM | 7:00 AM |
| 11:00 AM | 8:00 AM |
| 12:00 PM | 9:00 AM |
| 1:00 PM | 10:00 AM |
| 2:00 PM | 11:00 AM |
| 3:00 PM | 12:00 PM |
| 4:00 PM | 1:00 PM |
| 5:00 PM | 2:00 PM |
| 6:00 PM | 3:00 PM |
| 7:00 PM | 4:00 PM |
| 8:00 PM | 5:00 PM |
| 9:00 PM | 6:00 PM |
| 10:00 PM | 7:00 PM |
| 11:00 PM | 8:00 PM |
Best time for a meeting
Normal 9-to-5 working hours overlap for 5 hours on a weekday: 12:00 PM–5:00 PM GMT, which is 9:00 AM–2:00 PM ADT.
Comparing more than two places? The meeting planner lines up working hours for up to six cities.
Daylight saving time
UK time (GMT/BST)
- Oct 25, 2026: clocks go back 1 hour at 2:00 AM (UTC+1 → UTC±0)
- Mar 28, 2027: clocks go forward 1 hour at 1:00 AM (UTC±0 → UTC+1)
Atlantic Time (AST/ADT)
- Nov 1, 2026: clocks go back 1 hour at 2:00 AM (UTC−3 → UTC−4)
- Mar 14, 2027: clocks go forward 1 hour at 2:00 AM (UTC−4 → UTC−3)
Where these clocks are used
- UK time (GMT/BST): London, Edinburgh, Dublin and Lisbon keep the same clock. IANA zone
Europe/London. - Atlantic Time (AST/ADT): Nova Scotia, New Brunswick, Prince Edward Island. IANA zone
America/Halifax.
Questions
What time is it in AST when it is 9 AM GMT?
On Oct 23, 2026, 9:00 AM BST is 5:00 AM ADT. On other dates the answer can shift by an hour because of daylight saving time; the table of periods on this page gives each one.
How many hours behind GMT is AST?
It depends on the date. Oct 23, 2026 to Oct 25, 2026: AST is 4 hours behind. Oct 25, 2026 to Nov 1, 2026: AST is 3 hours behind. Nov 1, 2026 to Mar 14, 2027: AST is 4 hours behind. Mar 14, 2027 to Mar 28, 2027: AST is 3 hours behind. Mar 28, 2027 onwards: AST is 4 hours behind.
Do GMT and AST observe daylight saving time?
UK time switches to BST (UTC+1) in summer and back to GMT (UTC±0) in winter. Atlantic Time switches to ADT (UTC−3) in summer and back to AST (UTC−4) in winter.
What is the best time for a meeting between GMT and AST?
Normal 9-to-5 working hours overlap for 5 hours on a weekday: 12:00 PM–5:00 PM GMT, which is 9:00 AM–2:00 PM ADT.
Scheduling across time zones? Share one Caly booking link and every guest sees your free times in their own zone. Try Caly free
Related conversions
- AST to GMT (reverse)
- GMT to EST
- GMT to CST
- GMT to MST
- GMT to PST
- GMT to UTC
- GMT to CET
- GMT to IST
- GMT to SGT
- GMT to JST
- GMT to AEST
- GMT to AKST
- All time zones
Computed from the IANA time zone database on Oct 23, 2026. Live clocks and the converter use your browser's copy of the same data.