What is AST in BST?
British Time is 4 hours ahead
Atlantic Time is on UTC−3:00 and British Time is on UTC+1:00 right now. Both are on daylight saving, so their clocks read ADT and BST. The gap changes during the year — see below.
- Time in Halifax
- 11:55 pm
- Time in London
- 3:55 am
- Difference
- +4 h
- Next clock change
- October 25, 2026
Convert a time
BST — British Time
3:00 am
Wed, the next day
When the difference changes
Atlantic Time and British Time do not change their clocks on the same dates, so the gap between them is not the same all year. Most converters show only today’s figure. These are the periods ahead:
- Now – October 25, 2026British Time is 4 hours ahead
- October 25, 2026 – November 1, 2026British Time is 3 hours ahead
- November 1, 2026 – March 14, 2027British Time is 4 hours ahead
- March 14, 2027 – March 28, 2027British Time is 3 hours ahead
- March 28, 2027 – onwardsBritish Time is 4 hours ahead
Periods shorter than a day are not listed: both zones change at 2am in their own local time, so there are a few hours on each transition date when the gap is briefly something else.
Daylight saving
Atlantic Time
Clocks go back one hour at 2am local time, becoming AST.
British Time
Clocks go back one hour at 2am local time, becoming GMT.
AST to BST conversion table
Every hour of Tuesday, September 22, 2026, converted from Atlantic Time to British Time. 4 of the 24 hours fall on a different calendar day in London, which is marked.
- 12:00 am ADT
- 4:00 am BST
- 1:00 am ADT
- 5:00 am BST
- 2:00 am ADT
- 6:00 am BST
- 3:00 am ADT
- 7:00 am BST
- 4:00 am ADT
- 8:00 am BST
- 5:00 am ADT
- 9:00 am BST
- 6:00 am ADT
- 10:00 am BST
- 7:00 am ADT
- 11:00 am BST
- 8:00 am ADT
- 12:00 pm BST
- 9:00 am ADT
- 1:00 pm BST
- 10:00 am ADT
- 2:00 pm BST
- 11:00 am ADT
- 3:00 pm BST
- 12:00 pm ADT
- 4:00 pm BST
- 1:00 pm ADT
- 5:00 pm BST
- 2:00 pm ADT
- 6:00 pm BST
- 3:00 pm ADT
- 7:00 pm BST
- 4:00 pm ADT
- 8:00 pm BST
- 5:00 pm ADT
- 9:00 pm BST
- 6:00 pm ADT
- 10:00 pm BST
- 7:00 pm ADT
- 11:00 pm BST
- 8:00 pm ADT
- 12:00 am BST+1 day
- 9:00 pm ADT
- 1:00 am BST+1 day
- 10:00 pm ADT
- 2:00 am BST+1 day
- 11:00 pm ADT
- 3:00 am BST+1 day
Scheduling between the two
Working hours overlap from 9:00 am to 2:00 pm ADT, which is 1:00 pm to 6:00 pm BST. Anything inside that window falls in the normal working day at both ends.
A note on AST: it can also mean Arabia Standard Time (UTC+3). This page means Atlantic Time.
A note on BST: it can also mean Bangladesh Standard Time (UTC+6). This page means British Summer Time.
Atlantic Time (ADT) is used in Nova Scotia, New Brunswick and Puerto Rico
British Time (BST) is used in the whole United Kingdom. In winter the UK is on GMT; from late March to late October it is on BST, an hour ahead.