What is AST in GMT?
Greenwich Mean Time is 3 hours ahead
Atlantic Time is on UTC−3:00 and Greenwich Mean Time is on UTC+0:00 right now. Atlantic Time is on daylight saving, so its clocks read ADT. The gap changes during the year — see below.
- Time in Halifax
- 11:55 pm
- Time in Greenwich
- 2:55 am
- Difference
- +3 h
- Next clock change
- November 1, 2026
Convert a time
GMT — Greenwich Mean Time
2:00 am
Wed, the next day
When the difference changes
Atlantic Time and Greenwich Mean 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 – November 1, 2026Greenwich Mean Time is 3 hours ahead
- November 1, 2026 – March 14, 2027Greenwich Mean Time is 4 hours ahead
- March 14, 2027 – onwardsGreenwich Mean Time is 3 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.
Greenwich Mean Time
Greenwich Mean Time stays on GMT all year, so its offset from UTC never moves.
AST to GMT conversion table
Every hour of Tuesday, September 22, 2026, converted from Atlantic Time to Greenwich Mean Time. 3 of the 24 hours fall on a different calendar day in Greenwich, which is marked.
- 12:00 am ADT
- 3:00 am GMT
- 1:00 am ADT
- 4:00 am GMT
- 2:00 am ADT
- 5:00 am GMT
- 3:00 am ADT
- 6:00 am GMT
- 4:00 am ADT
- 7:00 am GMT
- 5:00 am ADT
- 8:00 am GMT
- 6:00 am ADT
- 9:00 am GMT
- 7:00 am ADT
- 10:00 am GMT
- 8:00 am ADT
- 11:00 am GMT
- 9:00 am ADT
- 12:00 pm GMT
- 10:00 am ADT
- 1:00 pm GMT
- 11:00 am ADT
- 2:00 pm GMT
- 12:00 pm ADT
- 3:00 pm GMT
- 1:00 pm ADT
- 4:00 pm GMT
- 2:00 pm ADT
- 5:00 pm GMT
- 3:00 pm ADT
- 6:00 pm GMT
- 4:00 pm ADT
- 7:00 pm GMT
- 5:00 pm ADT
- 8:00 pm GMT
- 6:00 pm ADT
- 9:00 pm GMT
- 7:00 pm ADT
- 10:00 pm GMT
- 8:00 pm ADT
- 11:00 pm GMT
- 9:00 pm ADT
- 12:00 am GMT+1 day
- 10:00 pm ADT
- 1:00 am GMT+1 day
- 11:00 pm ADT
- 2:00 am GMT+1 day
Scheduling between the two
Working hours overlap from 9:00 am to 3:00 pm ADT, which is 12:00 pm to 6:00 pm GMT. 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.
Atlantic Time (ADT) is used in Nova Scotia, New Brunswick and Puerto Rico
Greenwich Mean Time (GMT) is used in as a fixed UTC+0 offset. Note that the UK itself leaves GMT every summer — see British Time below.