Offset
The time difference between Adelaide and Mountain Time is 15.5 hours.
Adelaide (ACST) is ahead of Mountain Time (MDT).
ACST: UTC+9:30
MDT: UTC-6
Mountain Time is currently observing daylight saving time; Adelaide is not.
When to schedule
Standard business hours (9 AM–5 PM, Mon–Fri) in Adelaide and Mountain Time don't overlap on the same weekday. Mountain Time is 15 hours behind Adelaide.
Realistic options: hand off asynchronously, or stretch one side by an hour to catch the other team at the start or end of their day.
This window may shift by an hour during daylight saving time.
Public holidays in 2026
National public holidays can affect availability — a counterpart is likely off work on their own holidays, so it's worth planning meetings and deadlines around them.
Australia
- New Year's DayThu, Jan 1
- Australia DayMon, Jan 26
- Good FridayFri, Apr 3
- Easter MondayMon, Apr 6
- Christmas DayFri, Dec 25
- St. Stephen's DayMon, Dec 28
United States
- New Year's DayThu, Jan 1
- Martin Luther King, Jr. DayMon, Jan 19
- Presidents DayMon, Feb 16
- Memorial DayMon, May 25
- Juneteenth National Independence DayFri, Jun 19
- Independence DayFri, Jul 3
- Labour DayMon, Sep 7
- Columbus DayMon, Oct 12
- Veterans DayWed, Nov 11
- Thanksgiving DayThu, Nov 26
- Christmas DayFri, Dec 25
About these zones
Adelaide uses Australian Central Time (ACST, or ACDT). To call Australia, dial +61.
Mountain Time is also known as MST, or MDT. To call United States, dial +1.
Mountain Time is approximately 9,000 miles northeast of Adelaide.
Quick reference
Full 24-hour conversion table — tap any time to open it in the converter.
| Adelaide | MST | Day |
|---|---|---|
| 12:00 am | 8:30 am | -1 day |
| 1:00 am | 9:30 am | -1 day |
| 2:00 am | 10:30 am | -1 day |
| 3:00 am | 11:30 am | -1 day |
| 4:00 am | 12:30 pm | -1 day |
| 5:00 am | 1:30 pm | -1 day |
| 6:00 am | 2:30 pm | -1 day |
| 7:00 am | 3:30 pm | -1 day |
| 8:00 am | 4:30 pm | -1 day |
| 9:00 am | 5:30 pm | -1 day |
| 10:00 am | 6:30 pm | -1 day |
| 11:00 am | 7:30 pm | -1 day |
| 12:00 pm | 8:30 pm | -1 day |
| 1:00 pm | 9:30 pm | -1 day |
| 2:00 pm | 10:30 pm | -1 day |
| 3:00 pm | 11:30 pm | -1 day |
| 4:00 pm | 12:30 am | Same day |
| 5:00 pm | 1:30 am | Same day |
| 6:00 pm | 2:30 am | Same day |
| 7:00 pm | 3:30 am | Same day |
| 8:00 pm | 4:30 am | Same day |
| 9:00 pm | 5:30 am | Same day |
| 10:00 pm | 6:30 am | Same day |
| 11:00 pm | 7:30 am | Same day |
Daylight saving time
Both zones observe daylight saving time, but they transition on different dates.
Adelaide: next transition on Sunday, October 4, 2026.
Mountain Time: next transition on Sunday, November 1, 2026.
Adelaide and Mountain Time are in opposite hemispheres, so their clocks change in opposite directions about six months apart — one springs forward while the other falls back. The offset between them therefore shifts twice a year and can swing by up to two hours across the seasons, more than a typical same-hemisphere pair. Recurring meetings will need re-checking after each transition.
See the daylight saving time page for transition dates across every time zone.
Daylight today
- Sunrise
- 7:20 AM
- Sunset
- 5:12 PM
- Day length
- 9h 52m
- Sunrise
- 5:33 AM
- Sunset
- 8:27 PM
- Day length
- 14h 54m
Daylight overlap: 4h 37m — 7:20 AM–11:57 AM in Adelaide (3:50 PM–8:27 PM in Mountain Time). Both locations are in daylight during this window.
Cities in these zones
Cities in Mountain Time
Browse all cities to see the current local time anywhere.
Airports in these zones
Airports in Australian Central Time
- ADL
Airports in Mountain Time
- BJC
- DEN
- OGD
- SLC
Related conversions
Common conversions
- What is 9:00 am Adelaide in MST?
- 9:00 am Adelaide is 5:30 pm MST, the previous day.
- What is 12:00 pm Adelaide in MST?
- 12:00 pm Adelaide is 8:30 pm MST, the previous day.
- What is 12:30 pm Adelaide in MST?
- 12:30 pm Adelaide is 9:00 pm MST, the previous day.
- What is 2:00 pm Adelaide in MST?
- 2:00 pm Adelaide is 10:30 pm MST, the previous day.
- What is 5:00 pm Adelaide in MST?
- 5:00 pm Adelaide is 1:30 am MST.
- What is 11:30 pm Adelaide in MST?
- 11:30 pm Adelaide is 8:00 am MST.