Convert ACST to HST
HST is 19 hours 30 minutes behind ACST. ACST is UTC+9:30 and HST is UTC−10.
Right now: ACST · HST
Best time to schedule a meeting
Standard 9–5 working hours do not overlap at all between ACST and HST. Someone has to take an early or late call — or use asynchronous communication instead.
| ACST | HST | Suitable? |
|---|---|---|
| 9:00 AM | 1:30 PM (previous day) | outside 9–5 |
| 10:00 AM | 2:30 PM (previous day) | outside 9–5 |
| 11:00 AM | 3:30 PM (previous day) | outside 9–5 |
| 12:00 PM | 4:30 PM (previous day) | outside 9–5 |
| 1:00 PM | 5:30 PM (previous day) | outside 9–5 |
| 2:00 PM | 6:30 PM (previous day) | outside 9–5 |
| 3:00 PM | 7:30 PM (previous day) | outside 9–5 |
| 4:00 PM | 8:30 PM (previous day) | outside 9–5 |
| 5:00 PM | 9:30 PM (previous day) | outside 9–5 |
ACST to HST conversion table
| ACST | HST |
|---|---|
| 12:00 AM | 4:30 AM (previous day) |
| 1:00 AM | 5:30 AM (previous day) |
| 2:00 AM | 6:30 AM (previous day) |
| 3:00 AM | 7:30 AM (previous day) |
| 4:00 AM | 8:30 AM (previous day) |
| 5:00 AM | 9:30 AM (previous day) |
| 6:00 AM | 10:30 AM (previous day) |
| 7:00 AM | 11:30 AM (previous day) |
| 8:00 AM | 12:30 PM (previous day) |
| 9:00 AM | 1:30 PM (previous day) |
| 10:00 AM | 2:30 PM (previous day) |
| 11:00 AM | 3:30 PM (previous day) |
| 12:00 PM | 4:30 PM (previous day) |
| 1:00 PM | 5:30 PM (previous day) |
| 2:00 PM | 6:30 PM (previous day) |
| 3:00 PM | 7:30 PM (previous day) |
| 4:00 PM | 8:30 PM (previous day) |
| 5:00 PM | 9:30 PM (previous day) |
| 6:00 PM | 10:30 PM (previous day) |
| 7:00 PM | 11:30 PM (previous day) |
| 8:00 PM | 12:30 AM |
| 9:00 PM | 1:30 AM |
| 10:00 PM | 2:30 AM |
| 11:00 PM | 3:30 AM |
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.
About HST
Hawaii Standard Time (HST) is UTC−10. It is used in Hawaii, which does not observe daylight saving at all.
Hawaii–Aleutian Standard Time is UTC−10 and Hawaii does not observe daylight saving. That makes it the North American zone whose relationship to everywhere else changes twice a year without it doing anything: Hawaii is two hours behind Los Angeles in winter and three in summer. It is also far enough west that the working day barely overlaps with the US east coast at all.
Does this gap change with the seasons?
Neither ACST nor HST shifts with the seasons, so this 19.5-hour difference holds all year. That is unusual enough to be worth relying on: most cross-continental gaps move twice a year.
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 ACST in HST?
9:00 AM ACST is 1:30 PM HST (previous day).
Is HST ahead of ACST?
HST is 19 hours 30 minutes behind ACST.
Which time zone does this use?
ACST is UTC+9:30 and HST is UTC−10. 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.