AST to BST Time Converter
BST is 4 hours ahead of AST. Atlantic Canada and the Caribbean are currently on ADT (UTC-3:00), and BST is UTC+1:00.
Best Time to Call Between AST and BST
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 BST. That's a 4-hour window.
both at work AST only BST only neither — hours along the strip are AST.
Common Times Converted
AST on the left, BST on the right.
AST to BST: Full 24-Hour Conversion Table
Shaded rows are working hours; the darker shade marks the hours when both zones are at work.
| AST | BST | 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 | BST only |
| 6:00 AM | 10:00 AM | BST only |
| 7:00 AM | 11:00 AM | BST only |
| 8:00 AM | 12:00 PM | BST 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 BST 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.
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.
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 BST
Frequently Asked Questions
What is the time difference between AST and BST?
BST is 4 hours ahead of AST. That is the live figure. Taken strictly as written, the gap between AST and BST is 5 hours — the two differ because at least one of these regions is currently on daylight saving.
What is 9:00 AM AST in BST?
9:00 AM AST is 1:00 PM BST.
What are the best hours to schedule a call between AST and BST?
Between 9:00 AM and 1:00 PM AST, which is 1:00 PM to 5:00 PM BST. Both sides are inside normal business hours through that window.
Does the difference between AST and BST 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 BST always mean British Summer Time?
BST also stands for Bangladesh Standard Time (UTC+6). BDT is the clearer label for that one.