AST to GMT Time Converter
GMT is 4 hours ahead of AST. Atlantic Canada and the Caribbean are currently on ADT (UTC-3:00), and The UK and Ireland are currently on BST (UTC+1:00).
Best Time to Call Between AST and GMT
Both zones are inside normal business hours between 9:00 AM and 1:00 PM AST — that's 1:00 PM to 5:00 PM GMT. That's a 4-hour window.
both at work AST only GMT only neither — hours along the strip are AST.
Common Times Converted
AST on the left, GMT on the right.
AST to GMT: Full 24-Hour Conversion Table
Shaded rows are working hours; the darker shade marks the hours when both zones are at work.
| AST | GMT | Working hours |
|---|---|---|
| 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 | GMT only |
| 6:00 AM | 10:00 AM | GMT only |
| 7:00 AM | 11:00 AM | GMT only |
| 8:00 AM | 12:00 PM | GMT only |
| 9:00 AM | 1:00 PM | Both zones |
| 10:00 AM | 2:00 PM | Both zones |
| 11:00 AM | 3:00 PM | Both zones |
| 12:00 PM | 4:00 PM | Both zones |
| 1:00 PM | 5:00 PM | AST only |
| 2:00 PM | 6:00 PM | AST only |
| 3:00 PM | 7:00 PM | AST only |
| 4:00 PM | 8:00 PM | AST only |
| 5:00 PM | 9:00 PM | — |
| 6:00 PM | 10:00 PM | — |
| 7:00 PM | 11:00 PM | — |
| 8:00 PM | 12:00 AM next day | — |
| 9:00 PM | 1:00 AM next day | — |
| 10:00 PM | 2:00 AM next day | — |
| 11:00 PM | 3:00 AM next day | — |
What AST and GMT Actually Are
AST — Atlantic Standard Time
Halifax, San Juan, Santo Domingo, Bermuda. Standing at UTC-4:00 as written, and the region does change its clocks, so its live offset moves by an hour twice a year. The next change is on Sunday, November 1, 2026, to AST. AST also stands for Arabia Standard Time (UTC+3), used in Saudi Arabia, Iraq and Kuwait.
Atlantic Standard Time is the only North American zone whose name is more commonly associated, worldwide, with a completely different zone — Arabia Standard Time.
GMT — Greenwich Mean Time
The UK and Ireland in winter, plus Iceland, Portugal and much of West Africa. Standing at UTC as written, and the region does change its clocks, so its live offset moves by an hour twice a year. The next change is on Sunday, October 25, 2026, to GMT. Often used loosely as a synonym for UTC. They differ by less than a second, so for scheduling they are interchangeable.
Britain ran an experiment from 1968 to 1971 on permanent UTC+1, abandoning GMT entirely. It was scrapped after complaints about dark winter mornings in Scotland.
What This Means in Practice
Both sides change clocks, on different dates
Both regions observe daylight saving but do not switch on the same day, so for a week or two each spring and fall the gap between them is an hour different from the rest of the year. Those short windows are where recurring invitations quietly break.
Major Cities in Each Zone
Cities on AST
Cities on GMT
Frequently Asked Questions
What is the time difference between AST and GMT?
GMT is 4 hours ahead of AST.
What is 9:00 AM AST in GMT?
9:00 AM AST is 1:00 PM GMT.
What are the best hours to schedule a call between AST and GMT?
Between 9:00 AM and 1:00 PM AST, which is 1:00 PM to 5:00 PM GMT. Both sides are inside normal business hours through that window.
Does the difference between AST and GMT change during the year?
Yes. Both regions observe daylight saving, and they do not switch on the same dates, so the gap shifts by an hour at least twice a year. The next clock change is on Sunday, November 1, 2026.
Does AST always mean Atlantic Standard Time?
AST also stands for Arabia Standard Time (UTC+3), used in Saudi Arabia, Iraq and Kuwait.
Does GMT always mean Greenwich Mean Time?
Often used loosely as a synonym for UTC. They differ by less than a second, so for scheduling they are interchangeable.