Convert ACDT to HST
HST is 20 hours 30 minutes behind ACDT. ACDT is UTC+10:30 and HST is UTC−10.
Right now: ACDT · HST
Best time to schedule a meeting
Standard 9–5 working hours do not overlap at all between ACDT and HST. Someone has to take an early or late call — or use asynchronous communication instead.
| ACDT | HST | Suitable? |
|---|---|---|
| 9:00 AM | 12:30 PM (previous day) | outside 9–5 |
| 10:00 AM | 1:30 PM (previous day) | outside 9–5 |
| 11:00 AM | 2:30 PM (previous day) | outside 9–5 |
| 12:00 PM | 3:30 PM (previous day) | outside 9–5 |
| 1:00 PM | 4:30 PM (previous day) | outside 9–5 |
| 2:00 PM | 5:30 PM (previous day) | outside 9–5 |
| 3:00 PM | 6:30 PM (previous day) | outside 9–5 |
| 4:00 PM | 7:30 PM (previous day) | outside 9–5 |
| 5:00 PM | 8:30 PM (previous day) | outside 9–5 |
ACDT to HST conversion table
| ACDT | HST |
|---|---|
| 12:00 AM | 3:30 AM (previous day) |
| 1:00 AM | 4:30 AM (previous day) |
| 2:00 AM | 5:30 AM (previous day) |
| 3:00 AM | 6:30 AM (previous day) |
| 4:00 AM | 7:30 AM (previous day) |
| 5:00 AM | 8:30 AM (previous day) |
| 6:00 AM | 9:30 AM (previous day) |
| 7:00 AM | 10:30 AM (previous day) |
| 8:00 AM | 11:30 AM (previous day) |
| 9:00 AM | 12:30 PM (previous day) |
| 10:00 AM | 1:30 PM (previous day) |
| 11:00 AM | 2:30 PM (previous day) |
| 12:00 PM | 3:30 PM (previous day) |
| 1:00 PM | 4:30 PM (previous day) |
| 2:00 PM | 5:30 PM (previous day) |
| 3:00 PM | 6:30 PM (previous day) |
| 4:00 PM | 7:30 PM (previous day) |
| 5:00 PM | 8:30 PM (previous day) |
| 6:00 PM | 9:30 PM (previous day) |
| 7:00 PM | 10:30 PM (previous day) |
| 8:00 PM | 11:30 PM (previous day) |
| 9:00 PM | 12:30 AM |
| 10:00 PM | 1:30 AM |
| 11:00 PM | 2:30 AM |
About ACDT
Australian Central Daylight Time (ACDT) is UTC+10:30. It is used in Adelaide in summer.
Australian Central Daylight Time is UTC+10:30, what South Australia keeps from October to April. Darwin stays on ACST through the summer, so for those months two cities in the same nominal zone are an hour apart — the only reason to be precise about which of the two abbreviations a meeting invitation carries.
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 ACDT nor HST shifts with the seasons, so this 20.5-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 ACDT in HST?
9:00 AM ACDT is 12:30 PM HST (previous day).
Is HST ahead of ACDT?
HST is 20 hours 30 minutes behind ACDT.
Which time zone does this use?
ACDT is UTC+10:30 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.