What is ACST in MST?
Mountain Time is 15 hours 30 minutes behind
Australian Central Time is on UTC+9:30 and Mountain Time is on UTC−6:00 right now. Mountain Time is on daylight saving, so its clocks read MDT. The gap changes during the year — see below.
- Time in Adelaide
- 11:44 am
- Time in Denver
- 8:14 pm
- Difference
- −15:30 h
- Next clock change
- October 3, 2026
Convert a time
MDT — Mountain Time
7:30 pm
Tue, the previous day
When the difference changes
Australian Central Time and Mountain 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 3, 2026Mountain Time is 15 hours 30 minutes behind
- October 3, 2026 – November 1, 2026Mountain Time is 16 hours 30 minutes behind
- November 1, 2026 – March 14, 2027Mountain Time is 17 hours 30 minutes behind
- March 14, 2027 – April 3, 2027Mountain Time is 16 hours 30 minutes behind
- April 3, 2027 – October 2, 2027Mountain Time is 15 hours 30 minutes behind
- October 2, 2027 – onwardsMountain Time is 16 hours 30 minutes 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
Australian Central Time
Clocks go forward one hour at 2am local time, becoming ACDT.
Mountain Time
Clocks go back one hour at 2am local time, becoming MST.
ACST to MST conversion table
Every hour of Wednesday, September 23, 2026, converted from Australian Central Time to Mountain Time. 16 of the 24 hours fall on a different calendar day in Denver, which is marked.
- 12:00 am ACST
- 8:30 am MDT−1 day
- 1:00 am ACST
- 9:30 am MDT−1 day
- 2:00 am ACST
- 10:30 am MDT−1 day
- 3:00 am ACST
- 11:30 am MDT−1 day
- 4:00 am ACST
- 12:30 pm MDT−1 day
- 5:00 am ACST
- 1:30 pm MDT−1 day
- 6:00 am ACST
- 2:30 pm MDT−1 day
- 7:00 am ACST
- 3:30 pm MDT−1 day
- 8:00 am ACST
- 4:30 pm MDT−1 day
- 9:00 am ACST
- 5:30 pm MDT−1 day
- 10:00 am ACST
- 6:30 pm MDT−1 day
- 11:00 am ACST
- 7:30 pm MDT−1 day
- 12:00 pm ACST
- 8:30 pm MDT−1 day
- 1:00 pm ACST
- 9:30 pm MDT−1 day
- 2:00 pm ACST
- 10:30 pm MDT−1 day
- 3:00 pm ACST
- 11:30 pm MDT−1 day
- 4:00 pm ACST
- 12:30 am MDT
- 5:00 pm ACST
- 1:30 am MDT
- 6:00 pm ACST
- 2:30 am MDT
- 7:00 pm ACST
- 3:30 am MDT
- 8:00 pm ACST
- 4:30 am MDT
- 9:00 pm ACST
- 5:30 am MDT
- 10:00 pm ACST
- 6:30 am MDT
- 11:00 pm ACST
- 7:30 am MDT
Scheduling between the two
Working hours overlap from 9:00 am to 10:00 am ACST, which is 5:30 pm to 6:30 pm MDT. Anything inside that window falls in the normal working day at both ends.
Australian Central Time (ACST) is used in South Australia and the Northern Territory, on a half-hour offset from the east coast
Mountain Time (MDT) is used in Salt Lake City, Albuquerque and Calgary. Arizona keeps MST all year and does not follow MDT.