Convert IRST to ACST
ACST is 6 hours ahead of IRST. IRST is UTC+3:30 and ACST is UTC+9:30.
Right now: IRST · ACST
Best time to schedule a meeting
Standard 9–5 working hours overlap for 2 hours: 9:00 AM–11:00 AM IRST (3:00 PM–5:00 PM ACST). Schedule meetings inside that window.
| IRST | ACST | Suitable? |
|---|---|---|
| 9:00 AM | 3:00 PM | working hours |
| 10:00 AM | 4:00 PM | working hours |
| 11:00 AM | 5:00 PM | outside 9–5 |
| 12:00 PM | 6:00 PM | outside 9–5 |
| 1:00 PM | 7:00 PM | outside 9–5 |
| 2:00 PM | 8:00 PM | outside 9–5 |
| 3:00 PM | 9:00 PM | outside 9–5 |
| 4:00 PM | 10:00 PM | outside 9–5 |
| 5:00 PM | 11:00 PM | outside 9–5 |
IRST to ACST conversion table
| IRST | ACST |
|---|---|
| 12:00 AM | 6:00 AM |
| 1:00 AM | 7:00 AM |
| 2:00 AM | 8:00 AM |
| 3:00 AM | 9:00 AM |
| 4:00 AM | 10:00 AM |
| 5:00 AM | 11:00 AM |
| 6:00 AM | 12:00 PM |
| 7:00 AM | 1:00 PM |
| 8:00 AM | 2:00 PM |
| 9:00 AM | 3:00 PM |
| 10:00 AM | 4:00 PM |
| 11:00 AM | 5:00 PM |
| 12:00 PM | 6:00 PM |
| 1:00 PM | 7:00 PM |
| 2:00 PM | 8:00 PM |
| 3:00 PM | 9:00 PM |
| 4:00 PM | 10:00 PM |
| 5:00 PM | 11:00 PM |
| 6:00 PM | 12:00 AM (next day) |
| 7:00 PM | 1:00 AM (next day) |
| 8:00 PM | 2:00 AM (next day) |
| 9:00 PM | 3:00 AM (next day) |
| 10:00 PM | 4:00 AM (next day) |
| 11:00 PM | 5:00 AM (next day) |
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 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 IRST nor ACST shifts with the seasons, so this 6-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 ACST?
9:00 AM IRST is 3:00 PM ACST.
Is ACST ahead of IRST?
ACST is 6 hours ahead of IRST.
Which time zone does this use?
IRST is UTC+3:30 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.