Convert MST to ACST
ACST is 16 hours 30 minutes ahead of MST. MST is UTC−7 and ACST is UTC+9:30.
Right now: MST · ACST
Best time to schedule a meeting
Standard 9–5 working hours do not overlap at all between MST and ACST. Someone has to take an early or late call — or use asynchronous communication instead.
| MST | ACST | Suitable? |
|---|---|---|
| 9:00 AM | 1:30 AM (next day) | outside 9–5 |
| 10:00 AM | 2:30 AM (next day) | outside 9–5 |
| 11:00 AM | 3:30 AM (next day) | outside 9–5 |
| 12:00 PM | 4:30 AM (next day) | outside 9–5 |
| 1:00 PM | 5:30 AM (next day) | outside 9–5 |
| 2:00 PM | 6:30 AM (next day) | outside 9–5 |
| 3:00 PM | 7:30 AM (next day) | outside 9–5 |
| 4:00 PM | 8:30 AM (next day) | outside 9–5 |
| 5:00 PM | 9:30 AM (next day) | outside 9–5 |
MST to ACST conversion table
| MST | ACST |
|---|---|
| 12:00 AM | 4:30 PM |
| 1:00 AM | 5:30 PM |
| 2:00 AM | 6:30 PM |
| 3:00 AM | 7:30 PM |
| 4:00 AM | 8:30 PM |
| 5:00 AM | 9:30 PM |
| 6:00 AM | 10:30 PM |
| 7:00 AM | 11:30 PM |
| 8:00 AM | 12:30 AM (next day) |
| 9:00 AM | 1:30 AM (next day) |
| 10:00 AM | 2:30 AM (next day) |
| 11:00 AM | 3:30 AM (next day) |
| 12:00 PM | 4:30 AM (next day) |
| 1:00 PM | 5:30 AM (next day) |
| 2:00 PM | 6:30 AM (next day) |
| 3:00 PM | 7:30 AM (next day) |
| 4:00 PM | 8:30 AM (next day) |
| 5:00 PM | 9:30 AM (next day) |
| 6:00 PM | 10:30 AM (next day) |
| 7:00 PM | 11:30 AM (next day) |
| 8:00 PM | 12:30 PM (next day) |
| 9:00 PM | 1:30 PM (next day) |
| 10:00 PM | 2:30 PM (next day) |
| 11:00 PM | 3:30 PM (next day) |
About MST
Mountain Standard Time (MST) is UTC−7. It is used in Denver and Salt Lake City in winter, and Phoenix all year.
Mountain Standard Time is UTC−7. Denver and Salt Lake City use it in winter and switch to MDT in summer; Arizona does not switch at all and stays on MST year-round, which means Phoenix agrees with Denver in winter and with Los Angeles in summer. The Navajo Nation, inside Arizona, does observe daylight saving, so the state contains both. Any scheduling system that maps "Arizona" to "Mountain Time" without the no-DST flag will be an hour out for eight months.
About ACST
Australian Central Standard Time (ACST) is UTC+9:30. It is used in Adelaide and Darwin in winter.
Australian Central Standard Time is UTC+9:30, half an hour behind the eastern states rather than a whole hour, which surprises people every time. South Australia moves to daylight saving in October and the Northern Territory does not, so Adelaide and Darwin share this offset for half the year and are an hour apart for the other half.
Does this gap change with the seasons?
This gap is seasonal. The abbreviations themselves are fixed offsets, but the region on MST switches to MDT (UTC−6) from March to November. So the 16.5-hour figure on this page is correct for the part of the year when both places are actually on these abbreviations, and changes by an hour outside it.
ACST does not shift, so the whole change comes from one side. A recurring meeting fixed in ACST will appear to move by an hour for everyone on the other side, twice a year, without anyone changing anything.
This is the reason scheduling systems store an IANA zone such as Region/City rather than an offset or an abbreviation: the zone knows its own rules and the offset does not.
Frequently asked questions
What time is 9:00 AM MST in ACST?
9:00 AM MST is 1:30 AM ACST (next day).
Is ACST ahead of MST?
ACST is 16 hours 30 minutes ahead of MST.
Which time zone does this use?
MST is UTC−7 and ACST is UTC+9:30. Both abbreviations denote a single fixed offset, so this conversion never shifts with daylight saving — what changes is which abbreviation a place is using at the time.