BST to AST Time Converter
AST is 4 hours behind BST. BST is UTC+1:00, and Atlantic Canada and the Caribbean are currently on ADT (UTC-3:00).
Best Time to Call Between BST and AST
Both zones are inside normal business hours between 1:00 PM and 5:00 PM BST — that's 9:00 AM to 1:00 PM AST. That's a 4-hour window.
both at work BST only AST only neither — hours along the strip are BST.
Common Times Converted
BST on the left, AST on the right.
BST to AST: Full 24-Hour Conversion Table
Shaded rows are working hours; the darker shade marks the hours when both zones are at work.
| BST | AST | Working hours |
|---|---|---|
| 12:00 AM | 8:00 PM prev day | — |
| 1:00 AM | 9:00 PM prev day | — |
| 2:00 AM | 10:00 PM prev day | — |
| 3:00 AM | 11:00 PM prev day | — |
| 4:00 AM | 12:00 AM | — |
| 5:00 AM | 1:00 AM | — |
| 6:00 AM | 2:00 AM | — |
| 7:00 AM | 3:00 AM | — |
| 8:00 AM | 4:00 AM | — |
| 9:00 AM | 5:00 AM | BST only |
| 10:00 AM | 6:00 AM | BST only |
| 11:00 AM | 7:00 AM | BST only |
| 12:00 PM | 8:00 AM | BST only |
| 1:00 PM | 9:00 AM | Both zones |
| 2:00 PM | 10:00 AM | Both zones |
| 3:00 PM | 11:00 AM | Both zones |
| 4:00 PM | 12:00 PM | Both zones |
| 5:00 PM | 1:00 PM | AST only |
| 6:00 PM | 2:00 PM | AST only |
| 7:00 PM | 3:00 PM | AST only |
| 8:00 PM | 4:00 PM | AST only |
| 9:00 PM | 5:00 PM | — |
| 10:00 PM | 6:00 PM | — |
| 11:00 PM | 7:00 PM | — |
What BST and AST Actually Are
BST — British Summer Time
London, Manchester, Birmingham, Glasgow, and the rest of the UK from late March to late October. Standing at UTC+1:00 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, October 25, 2026, to GMT. BST also stands for Bangladesh Standard Time (UTC+6). BDT is the clearer label for that one.
British Summer Time began in 1916 as a wartime fuel-saving measure and has run every year since, making it one of the oldest continuous daylight saving schemes in the world.
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.
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 BST
Cities on AST
Frequently Asked Questions
What is the time difference between BST and AST?
AST is 4 hours behind BST. That is the live figure. Taken strictly as written, the gap between BST and AST is 5 hours — the two differ because at least one of these regions is currently on daylight saving.
What is 9:00 AM BST in AST?
9:00 AM BST is 5:00 AM AST.
What are the best hours to schedule a call between BST and AST?
Between 1:00 PM and 5:00 PM BST, which is 9:00 AM to 1:00 PM AST. Both sides are inside normal business hours through that window.
Does the difference between BST and AST 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, October 25, 2026.
Does BST always mean British Summer Time?
BST also stands for Bangladesh Standard Time (UTC+6). BDT is the clearer label for that one.
Does AST always mean Atlantic Standard Time?
AST also stands for Arabia Standard Time (UTC+3), used in Saudi Arabia, Iraq and Kuwait.