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DateAlmanac

What is ACST in AST?

Atlantic Time is 12 hours 30 minutes behind

Australian Central Time is on UTC+9:30 and Atlantic Time is on UTC−3:00 right now. Atlantic Time is on daylight saving, so its clocks read ADT. The gap changes during the year — see below.

Time in Adelaide
9:33:42 PM
Time in Halifax
9:03:42 AM
Difference
−12:30 h
Next clock change
October 4, 2026

Convert a time

ADT — Atlantic Time

8:30 am

ADT, Fri

When the difference changes

Australian Central 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:

  1. Now – October 4, 2026Atlantic Time is 12 hours 30 minutes behind
  2. October 4, 2026 – November 1, 2026Atlantic Time is 13 hours 30 minutes behind
  3. November 1, 2026 – March 14, 2027Atlantic Time is 14 hours 30 minutes behind
  4. March 14, 2027 – April 4, 2027Atlantic Time is 13 hours 30 minutes behind
  5. April 4, 2027 – October 3, 2027Atlantic Time is 12 hours 30 minutes behind
  6. October 3, 2027 – onwardsAtlantic Time is 13 hours 30 minutes behind

Periods shorter than a day are not listed. Each zone changes at its own local time, so on a date when both move there are a few hours when the gap is briefly something else.

Daylight saving

Australian Central Time

Sunday, October 4, 2026

Clocks go forward one hour — 2:00 am becomes 3:00 am local time, and the zone is on ACDT after that.

Atlantic Time

Sunday, November 1, 2026

Clocks go back one hour — 2:00 am becomes 1:00 am local time, and the zone is on AST after that.

ACST to AST conversion table

Every hour of Friday, September 25, 2026, converted from Australian Central Time to Atlantic Time. 13 of the 24 hours fall on a different calendar day in Halifax, which is marked.

12:00 am ACST
11:30 am ADT−1 day
1:00 am ACST
12:30 pm ADT−1 day
2:00 am ACST
1:30 pm ADT−1 day
3:00 am ACST
2:30 pm ADT−1 day
4:00 am ACST
3:30 pm ADT−1 day
5:00 am ACST
4:30 pm ADT−1 day
6:00 am ACST
5:30 pm ADT−1 day
7:00 am ACST
6:30 pm ADT−1 day
8:00 am ACST
7:30 pm ADT−1 day
9:00 am ACST
8:30 pm ADT−1 day
10:00 am ACST
9:30 pm ADT−1 day
11:00 am ACST
10:30 pm ADT−1 day
12:00 pm ACST
11:30 pm ADT−1 day
1:00 pm ACST
12:30 am ADT
2:00 pm ACST
1:30 am ADT
3:00 pm ACST
2:30 am ADT
4:00 pm ACST
3:30 am ADT
5:00 pm ACST
4:30 am ADT
6:00 pm ACST
5:30 am ADT
7:00 pm ACST
6:30 am ADT
8:00 pm ACST
7:30 am ADT
9:00 pm ACST
8:30 am ADT
10:00 pm ACST
9:30 am ADT
11:00 pm ACST
10:30 am ADT

Scheduling between the two

There is no overlap between a nine-to-six working day in Adelaide and one in Halifax — the gap is too wide. A call has to sit early or late for one side. Early morning in Adelaide is the usual compromise, since that is late afternoon or evening in Halifax.

A note on AST: it can also mean Arabia Standard Time (UTC+3). This page means Atlantic Time.

Australian Central Time (ACST) is used in South Australia and the Northern Territory, on a half-hour offset from the east coast

Atlantic Time (ADT) is used in Nova Scotia, New Brunswick and Puerto Rico

Other conversions