AST to BST: AST is 4 hours behind BST

Atlantic Time is 4 hours behind UK Time right now. It is 12:21 am ADT in Atlantic and 4:21 am BST in UK.

Convert a specific time from AST to BST

Pick any time and date to convert it both ways. The conversion runs in your browser against the real zone rules, so a date inside a daylight saving period gets that period's offset rather than today's.

What is the time difference between AST and BST?

UK Time is 4 hours ahead of Atlantic Time. To go from AST to BST you add 4 hours. That gap is not fixed. Across 2026 the distance between these two zones takes 2 different values, from 3 hours to 4 hours, because the two sides change their clocks on different dates. This page recomputes it rather than assuming.

AST to BST conversion table

Every hour of Friday, September 25, 2026 in Atlantic, with the matching reading in UK. 4 of the 24 hours land on a different calendar date in UK, which is the part people get wrong when they schedule across this pair.

What are the best hours to schedule a call between AST and BST?

4 hours of the standard 9:00 am to 5:00 pm working day line up in both zones, from 9:00 am AST to 1:00 pm AST. In UK that window reads 1:00 pm to 5:00 pm. Outside it, one side is either not yet at their desk or already gone.

Does daylight saving change AST to BST?

Atlantic Time is currently on ADT and changes next on Sunday, November 1, 2026, when the clock falls back from 1:59 am to 1:00 am and the offset moves from UTC-3 to UTC-4.

UK Time is currently on BST and changes next on Sunday, October 25, 2026, when the clock falls back from 1:59 am to 1:00 am and the offset moves from UTC+1 to UTC+0.

Because the two sides do not move together, the answer to this conversion changes during the year. The United States changes on the second Sunday in March and the first Sunday in November, while the United Kingdom and European Union change on the last Sunday in March and the last Sunday in October. Those dates are weeks apart, which opens a window each spring and autumn where the usual gap is an hour out. The table above is built for today, not for an average day.

Is AST ahead of or behind BST?

AST is behind BST by 4 hours: when it is 12:00 pm in Atlantic, it is 4:00 pm in UK. One wrinkle worth knowing: AST and ADT are two names for the same zone, not two zones. Atlantic Time reads AST in winter and ADT in summer. When somebody types "ast to bst" they nearly always mean the zone rather than the literal winter offset, so this page resolves AST to America/Halifax and BST to Europe/London and applies whichever offset is genuinely in force on the day.

Atlantic Time covers Halifax, Moncton and the Canadian Maritimes. UK Time covers London, Cardiff, Edinburgh and Dublin. The identifiers behind them are America/Halifax and Europe/London, which is what any calendar or scheduling system should be storing rather than a fixed number of hours.

Questions

What is AST in BST?

AST is 4 hours behind BST. 9:00 am AST is 1:00 pm BST.

How many hours ahead is BST of AST?

BST is 4 hours ahead of AST. That varies across the year, between 3 hours and 4 hours.

What time is it in UK right now?

4:21 am BST on Friday, September 25, 2026.

When can Atlantic and UK meet during working hours?

Between 9:00 am and 1:00 pm AST, which is 1:00 pm to 5:00 pm BST.

Does this account for daylight saving?

Yes. Every reading is computed from the IANA database for the actual date, so ADT and BST are the abbreviations genuinely in force today rather than a fixed assumption.

Other conversions

All timezone conversions

12 and 24 hour converter · 8 hours from now · Today · Day counter