Convert HST to ACST
ACST is 19 hours 30 minutes ahead of HST. HST is UTC−10 and ACST is UTC+9:30.
Right now: HST · ACST
Best time to schedule a meeting
Standard 9–5 working hours do not overlap at all between HST and ACST. Someone has to take an early or late call — or use asynchronous communication instead.
| HST | ACST | Suitable? |
|---|---|---|
| 9:00 AM | 4:30 AM (next day) | outside 9–5 |
| 10:00 AM | 5:30 AM (next day) | outside 9–5 |
| 11:00 AM | 6:30 AM (next day) | outside 9–5 |
| 12:00 PM | 7:30 AM (next day) | outside 9–5 |
| 1:00 PM | 8:30 AM (next day) | outside 9–5 |
| 2:00 PM | 9:30 AM (next day) | outside 9–5 |
| 3:00 PM | 10:30 AM (next day) | outside 9–5 |
| 4:00 PM | 11:30 AM (next day) | outside 9–5 |
| 5:00 PM | 12:30 PM (next day) | outside 9–5 |
HST to ACST conversion table
| HST | ACST |
|---|---|
| 12:00 AM | 7:30 PM |
| 1:00 AM | 8:30 PM |
| 2:00 AM | 9:30 PM |
| 3:00 AM | 10:30 PM |
| 4:00 AM | 11:30 PM |
| 5:00 AM | 12:30 AM (next day) |
| 6:00 AM | 1:30 AM (next day) |
| 7:00 AM | 2:30 AM (next day) |
| 8:00 AM | 3:30 AM (next day) |
| 9:00 AM | 4:30 AM (next day) |
| 10:00 AM | 5:30 AM (next day) |
| 11:00 AM | 6:30 AM (next day) |
| 12:00 PM | 7:30 AM (next day) |
| 1:00 PM | 8:30 AM (next day) |
| 2:00 PM | 9:30 AM (next day) |
| 3:00 PM | 10:30 AM (next day) |
| 4:00 PM | 11:30 AM (next day) |
| 5:00 PM | 12:30 PM (next day) |
| 6:00 PM | 1:30 PM (next day) |
| 7:00 PM | 2:30 PM (next day) |
| 8:00 PM | 3:30 PM (next day) |
| 9:00 PM | 4:30 PM (next day) |
| 10:00 PM | 5:30 PM (next day) |
| 11:00 PM | 6:30 PM (next day) |
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.
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?
Neither HST nor ACST 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 HST in ACST?
9:00 AM HST is 4:30 AM ACST (next day).
Is ACST ahead of HST?
ACST is 19 hours 30 minutes ahead of HST.
Which time zone does this use?
HST is UTC−10 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.