Tehran to ACST
+6hTehran
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.
About Tehran
WikipediaTehran operates on Iran Standard Time (IRST), UTC+3:30. Iran's unique half-hour offset makes Tehran time distinctive for regional business coordination.
Iran Standard Time (IRST) is one of few timezones with a 30-minute offset (UTC+3:30).
Comparing Time Zones: Tehran and ACST
Tehran runs on Iran Standard Time (IRST) at UTC+03:30. ACST runs on Australian Central Standard Time (ACST) at UTC+09:30. That puts Tehran 6 hours ahead of ACST — a difference of +6h at the current offsets.
In practice, when it is 9:00 AM in Tehran it is 3:00 PM in ACST. Midnight in Tehran is 6:00 AM in ACST. Neither zone observes daylight saving time, so the offset between them stays constant all year.
Tehran to ACST time conversion table
| Tehran (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 Tehran to ACST time
- Scheduling a call from Tehran to ACST: a 10:00 AM start in Tehran lands at 4:00 PM in ACST, so you can confirm the slot without doing the arithmetic yourself.
- Finding shared working hours: both Tehran 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.
- Keeping family and friends in sync: knowing that 8:00 PM in Tehran is 2:00 AM in ACST makes it easy to avoid calling at 3 AM.
- 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 Tehran 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 Tehran and ACST
Both Tehran 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
Tehran and ACST overlap for about 2 hours during the working day — enough for meetings if you avoid the edges of the window.
Tehran 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
Tehran
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 Tehran and ACST?
Tehran (IRST, UTC+03:30) is 6 hours ahead of ACST (ACST, UTC+09:30). The gap is currently +6h.
How do I convert Tehran time to ACST time?
Add +6h to Tehran local time. For example, 9:00 AM in Tehran 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 Tehran.
What is the best time to call ACST from Tehran?
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, Tehran or ACST?
Tehran is 6 hours ahead of ACST. When it is 12:00 PM in Tehran it is 6:00 PM in ACST.
Do Tehran and ACST use different time zones?
Tehran (Iran) uses IRST at UTC+03:30, while ACST uses ACST at UTC+09:30. The IANA identifiers are Asia/Tehran and Australia/Adelaide.
Does daylight saving time affect the Tehran–ACST difference?
Neither zone observes daylight saving time, so the +6h offset between Tehran and ACST is fixed all year.
Which other cities share Tehran's time zone?
IRST also covers Tehran, Isfahan, Mashhad, Tabriz, Shiraz, Karaj.
Which countries use IRST, Tehran's zone?
IRST is used in Iran.
Is there a day difference between Tehran and ACST?
Not normally. The +6h gap only pushes the date over for late-evening times.
What is the time difference between Tehran and ACST?
ACST is +6h from Tehran.
What timezone is Tehran in?
Tehran operates on Iran Standard Time (IRST), UTC+3:30. Iran's unique half-hour offset makes Tehran time distinctive for regional business coordination.
What timezone is ACST in?
ACST operates on its local timezone.
What are the business hours in Tehran?
Standard business hours in Tehran are 8:00 AM - 4:00 PM IRST.
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 Tehran, what time is it in ACST?
When it is 12:00 AM (midnight) in Tehran (IRST), it is +6h later in ACST (ACST).
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