ACST to Tehran
-6hACST
ACSTSOURCETehran
IRSTGreen rows indicate typical business hours (9 AM - 5 PM)
ACST and IRST on the World Map
The map below highlights the ACST (Australian Central Standard Time) and IRST (Iran Standard Time) timezone regions across the globe.
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.
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.
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: ACST and Tehran
ACST runs on Australian Central Standard Time (ACST) at UTC+09:30. Tehran runs on Iran Standard Time (IRST) at UTC+03:30. That puts ACST 6 hours behind Tehran — a difference of -6h at the current offsets.
In practice, when it is 9:00 AM in ACST it is 3:00 AM in Tehran. Midnight in ACST is 6:00 PM in Tehran. Neither zone observes daylight saving time, so the offset between them stays constant all year.
ACST to Tehran time conversion table
| ACST (ACST) | Tehran (IRST) | Day |
|---|---|---|
| 12:00 AM | 6:00 PM | previous day |
| 6:00 AM | 12:00 AM | same day |
| 7:00 AM | 1:00 AM | same day |
| 8:00 AM | 2:00 AM | same day |
| 9:00 AM | 3:00 AM | same day |
| 12:00 PM | 6:00 AM | same day |
| 3:00 PM | 9:00 AM | same day |
| 5:00 PM | 11:00 AM | same day |
| 6:00 PM | 12:00 PM | same day |
| 9:00 PM | 3:00 PM | same day |
Why people convert ACST to Tehran time
- Scheduling a call from ACST to Tehran: a 10:00 AM start in ACST lands at 4:00 AM in Tehran, so you can confirm the slot without doing the arithmetic yourself.
- Finding shared working hours: both ACST and Tehran are inside the 9-to-5 working day between 3:00 PM and 5:00 PM ACST time (9:00 AM–11:00 AM IRST). That is roughly 2 hours of usable overlap.
- Watching a live event or market open: ACST viewers need 3:00 AM in Tehran to catch a 9:00 AM start there, and 6:00 AM if the event is anchored to ACST.
- Always state the zone abbreviation, not just the hour. "3:00 PM ACST" is unambiguous; "3 PM" across a -6h gap is not.
- Block 3:00 PM–5:00 PM ACST as the recurring meeting window if you work primarily from ACST and need Tehran colleagues present.
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.
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.
Best time to call between ACST and Tehran
Both ACST and Tehran sit inside the 9 AM – 5 PM working day between 3:00 PM–5:00 PM ACST, which is 9:00 AM–11:00 AM IRST. That gives roughly 2 hours of shared time — the safest window for a live call or meeting.
Business hours overlap
ACST and Tehran overlap for about 2 hours during the working day — enough for meetings if you avoid the edges of the window.
ACST is 6 hours behind Tehran (ACST UTC+09:30 → IRST UTC+03:30). The shared working window is 3:00 PM–5:00 PM ACST. Remember to re-check around daylight-saving transitions.
🕐 Daylight Saving Time Info
ACST
❄ Currently in Standard Time
Standard: UTC+09:30 · DST: UTC+10:30
Clocks spring forward on Sat, Oct 3, 2026
Tehran
Does not observe DST
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 ACST and Tehran?
ACST (ACST, UTC+09:30) is 6 hours behind Tehran (IRST, UTC+03:30). The gap is currently -6h.
How do I convert ACST time to Tehran time?
Add -6h to ACST local time. For example, 9:00 AM in ACST is 3:00 AM in Tehran.
What time is it in Tehran right now?
Tehran uses IRST at UTC+03:30. Use the live converter at the top of this page — it updates in real time and already accounts for the -6h offset from ACST.
What is the best time to call Tehran from ACST?
Call between 3:00 PM and 5:00 PM ACST — that maps to 9:00 AM–11:00 AM IRST and keeps both parties inside the working day.
Which is behind, ACST or Tehran?
ACST is 6 hours behind Tehran. When it is 12:00 PM in ACST it is 6:00 AM in Tehran.
Do ACST and Tehran use different time zones?
ACST uses ACST at UTC+09:30, while Tehran (Iran) uses IRST at UTC+03:30. The IANA identifiers are Australia/Adelaide and Asia/Tehran.
Does daylight saving time affect the ACST–Tehran difference?
Neither zone observes daylight saving time, so the -6h offset between ACST and Tehran is fixed all year.
Which other cities share ACST's time zone?
ACST also covers Adelaide, Darwin, Alice Springs, Mount Gambier.
Which countries use ACST, ACST's zone?
ACST is used in Australia (South Australia, Northern Territory).
Is there a day difference between ACST and Tehran?
Not normally. The -6h gap only pushes the date over the previous day.
What is the time difference between ACST and Tehran?
Tehran is -6h from ACST.
What timezone is ACST in?
ACST operates on its local timezone.
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 are the business hours in Tehran?
Standard business hours in Tehran are 8:00 AM - 4:00 PM IRST.
Which countries use ACST (Australian Central Standard Time)?
ACST is used in Australia (South Australia, Northern Territory).
Does ACST observe daylight saving time?
Yes, ACST switches to ACDT during summer months.
What are some interesting facts about ACST?
ACST uses a half-hour offset: UTC+09:30. South Australia moves to ACDT (UTC+10:30) in summer; the Northern Territory does not.
Which cities are in the IRST timezone?
Major cities in the IRST timezone include Tehran, Isfahan, Mashhad, Tabriz, Shiraz, Karaj.
What is the UTC offset for IRST?
Iran Standard Time (IRST) is at UTC+03:30. During daylight saving time, it shifts to IRDT.
What should I know about the IRST timezone?
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).
When is it midnight in ACST, what time is it in Tehran?
When it is 12:00 AM (midnight) in ACST (ACST), it is -6h later in Tehran (IRST).
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