IRST to AST
-7h 30mIRST
IRSTSOURCEAST
ASTGreen rows indicate typical business hours (9 AM - 5 PM)
IRST and AST on the World Map
The map below highlights the IRST (Iran Standard Time) and AST (Atlantic 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.
AST – Atlantic Standard Time
UTC-04:00Atlantic Standard Time (AST) is the time zone for the Canadian Atlantic provinces and the Caribbean, 4 hours behind UTC.
- •Puerto Rico uses AST year-round and does not observe DST.
- •AST is 1 hour ahead of EST.
- •Halifax, the capital of Nova Scotia, is the largest city in AST Canada.
IRST vs AST: Offsets, DST and Best Call Times
IRST runs on Iran Standard Time (IRST) at UTC+03:30. AST runs on Atlantic Standard Time (AST) at UTC-04:00. That puts IRST 7 hours 30 minutes behind AST — a difference of -7h 30m at the current offsets.
In practice, when it is 9:00 AM in IRST it is 1:30 AM in AST. Midnight in IRST is 4:30 PM in AST. Neither zone observes daylight saving time, so the offset between them stays constant all year.
IRST to AST time conversion table
| IRST (IRST) | AST (AST) | Day |
|---|---|---|
| 12:00 AM | 4:30 PM | previous day |
| 6:00 AM | 10:30 PM | previous day |
| 7:00 AM | 11:30 PM | previous day |
| 8:00 AM | 12:30 AM | same day |
| 9:00 AM | 1:30 AM | same day |
| 12:00 PM | 4:30 AM | same day |
| 3:00 PM | 7:30 AM | same day |
| 5:00 PM | 9:30 AM | same day |
| 6:00 PM | 10:30 AM | same day |
| 9:00 PM | 1:30 PM | same day |
Why people convert IRST to AST time
- Scheduling a call from IRST to AST: a 10:00 AM start in IRST lands at 2:30 AM in AST, so you can confirm the slot without doing the arithmetic yourself.
- Finding shared working hours: both IRST and AST are inside the 9-to-5 working day between 4:30 PM and 5:00 PM IRST time (9:00 AM–9:30 AM AST). That is roughly 0 hours 30 minutes of usable overlap.
- Keeping family and friends in sync: knowing that 8:00 PM in IRST is 12:30 PM in AST 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 -7h 30m gap is not.
- Block 4:30 PM–5:00 PM IRST as the recurring meeting window if you work primarily from IRST and need AST 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 AST (Atlantic Standard Time)
Atlantic Standard Time (AST) covers Canada's Atlantic provinces (Nova Scotia, New Brunswick, Prince Edward Island, and most of Labrador), as well as several Caribbean nations. Puerto Rico and the US Virgin Islands use AST year-round without daylight saving time. The Canadian provinces switch to Atlantic Daylight Time (ADT) in summer.
Best time to call between IRST and AST
Both IRST and AST sit inside the 9 AM – 5 PM working day between 4:30 PM–5:00 PM IRST, which is 9:00 AM–9:30 AM AST. That gives roughly 0 hours and 30 minutes of shared time — the safest window for a live call or meeting.
Business hours overlap
IRST and AST overlap for only 30 minutes (4:30 PM–5:00 PM IRST), so meetings have to be booked precisely.
IRST is 7 hours 30 minutes behind AST (IRST UTC+03:30 → AST UTC-04:00). The shared working window is 4:30 PM–5:00 PM IRST. Remember to re-check around daylight-saving transitions.
🕐 Daylight Saving Time Info
IRST
Does not observe DST
AST
☀ Currently in DST
Standard: UTC-04:00 · DST: UTC-03:00
Clocks fall back on Sun, Nov 1, 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 AST?
IRST (IRST, UTC+03:30) is 7 hours 30 minutes behind AST (AST, UTC-04:00). The gap is currently -7h 30m.
How do I convert IRST time to AST time?
Add -7h 30m to IRST local time. For example, 9:00 AM in IRST is 1:30 AM in AST.
What time is it in AST right now?
AST uses AST at UTC-04:00. Use the live converter at the top of this page — it updates in real time and already accounts for the -7h 30m offset from IRST.
What is the best time to call AST from IRST?
Call between 4:30 PM and 5:00 PM IRST — that maps to 9:00 AM–9:30 AM AST and keeps both parties inside the working day.
Which is behind, IRST or AST?
IRST is 7 hours 30 minutes behind AST. When it is 12:00 PM in IRST it is 4:30 AM in AST.
Does daylight saving time affect the IRST–AST difference?
Neither zone observes daylight saving time, so the -7h 30m offset between IRST and AST 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 AST?
Not normally. The -7h 30m gap only pushes the date over the previous day.
What is the time difference between IRST and AST?
AST is -7h 30m from IRST.
What timezone is IRST in?
IRST operates on its local timezone.
What timezone is AST in?
AST 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 AST timezone?
Major cities in the AST timezone include Halifax, San Juan, Santo Domingo, Caracas, La Paz, Fredericton, Charlottetown.
What is the UTC offset for AST?
Atlantic Standard Time (AST) is at UTC-04:00. During daylight saving time, it shifts to ADT.
What should I know about the AST timezone?
Puerto Rico uses AST year-round and does not observe DST. AST is 1 hour ahead of EST.
When is it midnight in IRST, what time is it in AST?
When it is 12:00 AM (midnight) in IRST (IRST), it is -7h 30m later in AST (AST).
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