Convert IRST to HST
HST is 13 hours 30 minutes behind IRST. IRST is UTC+3:30 and HST is UTC−10.
Right now: IRST · HST
Best time to schedule a meeting
Standard 9–5 working hours do not overlap at all between IRST and HST. Someone has to take an early or late call — or use asynchronous communication instead.
| IRST | HST | Suitable? |
|---|---|---|
| 9:00 AM | 7:30 PM (previous day) | outside 9–5 |
| 10:00 AM | 8:30 PM (previous day) | outside 9–5 |
| 11:00 AM | 9:30 PM (previous day) | outside 9–5 |
| 12:00 PM | 10:30 PM (previous day) | outside 9–5 |
| 1:00 PM | 11:30 PM (previous day) | outside 9–5 |
| 2:00 PM | 12:30 AM | outside 9–5 |
| 3:00 PM | 1:30 AM | outside 9–5 |
| 4:00 PM | 2:30 AM | outside 9–5 |
| 5:00 PM | 3:30 AM | outside 9–5 |
IRST to HST conversion table
| IRST | HST |
|---|---|
| 12:00 AM | 10:30 AM (previous day) |
| 1:00 AM | 11:30 AM (previous day) |
| 2:00 AM | 12:30 PM (previous day) |
| 3:00 AM | 1:30 PM (previous day) |
| 4:00 AM | 2:30 PM (previous day) |
| 5:00 AM | 3:30 PM (previous day) |
| 6:00 AM | 4:30 PM (previous day) |
| 7:00 AM | 5:30 PM (previous day) |
| 8:00 AM | 6:30 PM (previous day) |
| 9:00 AM | 7:30 PM (previous day) |
| 10:00 AM | 8:30 PM (previous day) |
| 11:00 AM | 9:30 PM (previous day) |
| 12:00 PM | 10:30 PM (previous day) |
| 1:00 PM | 11:30 PM (previous day) |
| 2:00 PM | 12:30 AM |
| 3:00 PM | 1:30 AM |
| 4:00 PM | 2:30 AM |
| 5:00 PM | 3:30 AM |
| 6:00 PM | 4:30 AM |
| 7:00 PM | 5:30 AM |
| 8:00 PM | 6:30 AM |
| 9:00 PM | 7:30 AM |
| 10:00 PM | 8:30 AM |
| 11:00 PM | 9:30 AM |
About IRST
Iran Standard Time (IRST) is UTC+3:30. It is used in Iran, all year.
Iran Standard Time is UTC+3:30. Iran ran daylight saving for decades and stopped in 2022, so material written before then puts the country half an hour further ahead in summer and is now wrong. Half-hour offsets are rare enough that scheduling tools sometimes round them, which turns a correct calculation into a thirty-minute error.
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 IRST nor HST shifts with the seasons, so this 13.5-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 IRST in HST?
9:00 AM IRST is 7:30 PM HST (previous day).
Is HST ahead of IRST?
HST is 13 hours 30 minutes behind IRST.
Which time zone does this use?
IRST is UTC+3:30 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.