What is BST in AST?
Atlantic Time is 4 hours behind
British Time is on UTC+1:00 and Atlantic Time is on UTC−3:00 right now. Both are on daylight saving, so their clocks read BST and ADT. The gap changes during the year — see below.
- Time in London
- 4:47 am
- Time in Halifax
- 12:47 am
- Difference
- −4 h
- Next clock change
- October 25, 2026
Convert a time
ADT — Atlantic Time
12:00 am
Wed
When the difference changes
British Time and Atlantic 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, 2026Atlantic Time is 4 hours behind
- October 25, 2026 – November 1, 2026Atlantic Time is 3 hours behind
- November 1, 2026 – March 14, 2027Atlantic Time is 4 hours behind
- March 14, 2027 – March 28, 2027Atlantic Time is 3 hours behind
- March 28, 2027 – onwardsAtlantic Time is 4 hours behind
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
British Time
Clocks go back one hour at 2am local time, becoming GMT.
Atlantic Time
Clocks go back one hour at 2am local time, becoming AST.
BST to AST conversion table
Every hour of Wednesday, September 23, 2026, converted from British Time to Atlantic Time. 4 of the 24 hours fall on a different calendar day in Halifax, which is marked.
- 12:00 am BST
- 8:00 pm ADT−1 day
- 1:00 am BST
- 9:00 pm ADT−1 day
- 2:00 am BST
- 10:00 pm ADT−1 day
- 3:00 am BST
- 11:00 pm ADT−1 day
- 4:00 am BST
- 12:00 am ADT
- 5:00 am BST
- 1:00 am ADT
- 6:00 am BST
- 2:00 am ADT
- 7:00 am BST
- 3:00 am ADT
- 8:00 am BST
- 4:00 am ADT
- 9:00 am BST
- 5:00 am ADT
- 10:00 am BST
- 6:00 am ADT
- 11:00 am BST
- 7:00 am ADT
- 12:00 pm BST
- 8:00 am ADT
- 1:00 pm BST
- 9:00 am ADT
- 2:00 pm BST
- 10:00 am ADT
- 3:00 pm BST
- 11:00 am ADT
- 4:00 pm BST
- 12:00 pm ADT
- 5:00 pm BST
- 1:00 pm ADT
- 6:00 pm BST
- 2:00 pm ADT
- 7:00 pm BST
- 3:00 pm ADT
- 8:00 pm BST
- 4:00 pm ADT
- 9:00 pm BST
- 5:00 pm ADT
- 10:00 pm BST
- 6:00 pm ADT
- 11:00 pm BST
- 7:00 pm ADT
Scheduling between the two
Working hours overlap from 1:00 pm to 6:00 pm BST, which is 9:00 am to 2:00 pm ADT. Anything inside that window falls in the normal working day at both ends.
A note on BST: it can also mean Bangladesh Standard Time (UTC+6). This page means British Summer Time.
A note on AST: it can also mean Arabia Standard Time (UTC+3). This page means Atlantic Time.
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.
Atlantic Time (ADT) is used in Nova Scotia, New Brunswick and Puerto Rico