IRST to ACST
+6hIRST
IRSTSOURCEACST
ACSTGreen rows indicate typical business hours (9 AM - 5 PM)
IRST and ACST on the World Map
The map below highlights the IRST (Iran Standard Time) and ACST (Australian Central Standard Time) timezone regions across the globe.
IRST – Iran Standard Time
UTC+03:30Iran Standard Time (IRST) is the time zone for Iran, 3 hours and 30 minutes ahead of UTC.
- •IRST is one of only a few time zones with a 30-minute offset.
- •Iran observes daylight saving time, switching to IRDT (UTC+04:30).
- •Tehran has a metropolitan population of over 16 million.
ACST – Australian Central Standard Time
UTC+09:30Australian Central Standard Time (ACST, UTC+09:30) covers South Australia and the Northern Territory, on a half-hour offset.
- •ACST uses a half-hour offset: UTC+09:30.
- •South Australia moves to ACDT (UTC+10:30) in summer; the Northern Territory does not.
- •Adelaide and Darwin are 30 minutes apart during daylight saving, level in winter.
- •Adelaide is one of the few major cities on a 30-minute offset.
Everything You Need to Know About IRST and ACST Time
IRST runs on Iran Standard Time (IRST) at UTC+03:30. ACST runs on Australian Central Standard Time (ACST) at UTC+09:30. That puts IRST 6 hours ahead of ACST — a difference of +6h at the current offsets.
In practice, when it is 9:00 AM in IRST it is 3:00 PM in ACST. Midnight in IRST is 6:00 AM in ACST. Neither zone observes daylight saving time, so the offset between them stays constant all year.
IRST to ACST time conversion table
| IRST (IRST) | ACST (ACST) | Day |
|---|---|---|
| 12:00 AM | 6:00 AM | same day |
| 6:00 AM | 12:00 PM | same day |
| 7:00 AM | 1:00 PM | same day |
| 8:00 AM | 2:00 PM | same day |
| 9:00 AM | 3:00 PM | same day |
| 12:00 PM | 6:00 PM | same day |
| 3:00 PM | 9:00 PM | same day |
| 5:00 PM | 11:00 PM | same day |
| 6:00 PM | 12:00 AM | next day |
| 9:00 PM | 3:00 AM | next day |
Why people convert IRST to ACST time
- Scheduling a call from IRST to ACST: a 10:00 AM start in IRST lands at 4:00 PM in ACST, so you can confirm the slot without doing the arithmetic yourself.
- Finding shared working hours: both IRST and ACST are inside the 9-to-5 working day between 9:00 AM and 11:00 AM IRST time (3:00 PM–5:00 PM ACST). That is roughly 2 hours of usable overlap.
- Booking travel or deliveries: tracking ACST local time against IRST keeps pickup windows and arrival estimates honest across the +6h offset.
- Always state the zone abbreviation, not just the hour. "3:00 PM IRST" is unambiguous; "3 PM" across a +6h gap is not.
- Block 9:00 AM–11:00 AM IRST as the recurring meeting window if you work primarily from IRST and need ACST colleagues present.
About IRST (Iran Standard Time)
Iran Standard Time (IRST) is one of the few time zones with a 30-minute offset. Iran observes daylight saving time (IRDT, UTC+04:30) from late March to late September. Tehran, the capital, is one of the largest cities in the Middle East.
About ACST (Australian Central Standard Time)
Australian Central Standard Time (ACST) is the half-hour offset of UTC+09:30 used across South Australia and the Northern Territory, taking in Adelaide and Darwin. South Australia moves to Australian Central Daylight Time (ACDT, UTC+10:30) from the first Sunday in October to the first Sunday in April, but the Northern Territory does not observe daylight saving — so Adelaide and Darwin sit 30 minutes apart in summer and level with each other in winter. The half-hour offset means Adelaide is 30 minutes behind Sydney in winter and level with it during daylight saving, which regularly catches out travellers and meeting planners.
Best time to call between IRST and ACST
Both IRST and ACST sit inside the 9 AM – 5 PM working day between 9:00 AM–11:00 AM IRST, which is 3:00 PM–5:00 PM ACST. That gives roughly 2 hours of shared time — the safest window for a live call or meeting.
Business hours overlap
IRST and ACST overlap for about 2 hours during the working day — enough for meetings if you avoid the edges of the window.
IRST is 6 hours ahead of ACST (IRST UTC+03:30 → ACST UTC+09:30). The shared working window is 9:00 AM–11:00 AM IRST. Remember to re-check around daylight-saving transitions.
🕐 Daylight Saving Time Info
IRST
Does not observe DST
ACST
❄ Currently in Standard Time
Standard: UTC+09:30 · DST: UTC+10:30
Clocks spring forward on Sat, Oct 3, 2026
Learn More About Time
Dive deeper into the fascinating world of timekeeping, time zones, and how they shape our global society:
Frequently Asked Questions
What is the time difference between IRST and ACST?
IRST (IRST, UTC+03:30) is 6 hours ahead of ACST (ACST, UTC+09:30). The gap is currently +6h.
How do I convert IRST time to ACST time?
Add +6h to IRST local time. For example, 9:00 AM in IRST is 3:00 PM in ACST.
What time is it in ACST right now?
ACST uses ACST at UTC+09:30. Use the live converter at the top of this page — it updates in real time and already accounts for the +6h offset from IRST.
What is the best time to call ACST from IRST?
Call between 9:00 AM and 11:00 AM IRST — that maps to 3:00 PM–5:00 PM ACST and keeps both parties inside the working day.
Which is ahead, IRST or ACST?
IRST is 6 hours ahead of ACST. When it is 12:00 PM in IRST it is 6:00 PM in ACST.
Does daylight saving time affect the IRST–ACST difference?
Neither zone observes daylight saving time, so the +6h offset between IRST and ACST is fixed all year.
Which other cities share IRST's time zone?
IRST also covers Tehran, Isfahan, Mashhad, Tabriz, Shiraz, Karaj.
Which countries use IRST, IRST's zone?
IRST is used in Iran.
Is there a day difference between IRST and ACST?
Not normally. The +6h gap only pushes the date over for late-evening times.
What is the time difference between IRST and ACST?
ACST is +6h from IRST.
What timezone is IRST in?
IRST operates on its local timezone.
What timezone is ACST in?
ACST operates on its local timezone.
Which countries use IRST (Iran Standard Time)?
IRST is used in Iran.
Does IRST observe daylight saving time?
Yes, IRST switches to IRDT during summer months.
What are some interesting facts about IRST?
IRST is one of only a few time zones with a 30-minute offset. Iran observes daylight saving time, switching to IRDT (UTC+04:30).
Which cities are in the ACST timezone?
Major cities in the ACST timezone include Adelaide, Darwin, Alice Springs, Mount Gambier.
What is the UTC offset for ACST?
Australian Central Standard Time (ACST) is at UTC+09:30. During daylight saving time, it shifts to ACDT.
What should I know about the ACST timezone?
ACST uses a half-hour offset: UTC+09:30. South Australia moves to ACDT (UTC+10:30) in summer; the Northern Territory does not.
When is it midnight in IRST, what time is it in ACST?
When it is 12:00 AM (midnight) in IRST (IRST), it is +6h later in ACST (ACST).
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See every conversion from IRST →·See every conversion from ACST →