IRST to BST
-2h 30mIRST
IRSTSOURCEBST
BSTGreen rows indicate typical business hours (9 AM - 5 PM)
IRST and BST on the World Map
The map below highlights the IRST (Iran Standard Time) and BST (British Summer 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.
BST – British Summer Time
UTC+01:00British Summer Time (BST, UTC+01:00) is the daylight saving period in the United Kingdom, running from late March to late October.
- •BST runs from the last Sunday in March to the last Sunday in October.
- •BST is exactly one hour ahead of GMT, the UK's standard time.
- •During BST, London is 4 hours ahead of New York while the US is on Eastern Daylight Time.
- •The Isle of Man and the Channel Islands also observe BST.
IRST to BST Time Difference – Complete Guide
IRST runs on Iran Standard Time (IRST) at UTC+03:30. BST runs on British Summer Time (BST) at UTC+01:00. That puts IRST 2 hours 30 minutes behind BST — a difference of -2h 30m at the current offsets.
In practice, when it is 9:00 AM in IRST it is 6:30 AM in BST. Midnight in IRST is 9:30 PM in BST. Neither zone observes daylight saving time, so the offset between them stays constant all year.
IRST to BST time conversion table
| IRST (IRST) | BST (BST) | Day |
|---|---|---|
| 12:00 AM | 9:30 PM | previous day |
| 6:00 AM | 3:30 AM | same day |
| 7:00 AM | 4:30 AM | same day |
| 8:00 AM | 5:30 AM | same day |
| 9:00 AM | 6:30 AM | same day |
| 12:00 PM | 9:30 AM | same day |
| 3:00 PM | 12:30 PM | same day |
| 5:00 PM | 2:30 PM | same day |
| 6:00 PM | 3:30 PM | same day |
| 9:00 PM | 6:30 PM | same day |
Why people convert IRST to BST time
- Scheduling a call from IRST to BST: a 10:00 AM start in IRST lands at 7:30 AM in BST, so you can confirm the slot without doing the arithmetic yourself.
- Finding shared working hours: both IRST and BST are inside the 9-to-5 working day between 11:30 AM and 5:00 PM IRST time (9:00 AM–2:30 PM BST). That is roughly 5 hours 30 minutes of usable overlap.
- Booking travel or deliveries: tracking BST local time against IRST keeps pickup windows and arrival estimates honest across the -2h 30m offset.
- Always state the zone abbreviation, not just the hour. "3:00 PM IRST" is unambiguous; "3 PM" across a -2h 30m gap is not.
- Block 11:30 AM–5:00 PM IRST as the recurring meeting window if you work primarily from IRST and need BST 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 BST (British Summer Time)
British Summer Time (BST) is the daylight saving period in the United Kingdom, when clocks move one hour forward from Greenwich Mean Time (GMT, UTC+00:00) to UTC+01:00. It runs from the last Sunday in March to the last Sunday in October. England, Scotland, Wales and Northern Ireland all follow it, along with the Isle of Man and the Channel Islands of Jersey and Guernsey. During BST, London is one hour ahead of UTC, four hours ahead of New York on Eastern Daylight Time, and five hours ahead of New York once the United States returns to Eastern Standard Time in November. BST is also used to abbreviate Bangladesh Standard Time (UTC+06:00), which is listed separately on this site.
Best time to call between IRST and BST
Both IRST and BST sit inside the 9 AM – 5 PM working day between 11:30 AM–5:00 PM IRST, which is 9:00 AM–2:30 PM BST. That gives roughly 5 hours and 30 minutes of shared time — the safest window for a live call or meeting.
Business hours overlap
IRST and BST share 5 hours of working-hours overlap (11:30 AM–5:00 PM IRST), so scheduling a live meeting is straightforward.
IRST is 2 hours 30 minutes behind BST (IRST UTC+03:30 → BST UTC+01:00). The shared working window is 11:30 AM–5:00 PM IRST. Remember to re-check around daylight-saving transitions.
🕐 Daylight Saving Time Info
IRST
Does not observe DST
BST
☀ Currently in DST
Standard: UTC+00:00 · DST: UTC+01:00
Clocks fall back on Sun, Oct 25, 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 BST?
IRST (IRST, UTC+03:30) is 2 hours 30 minutes behind BST (BST, UTC+01:00). The gap is currently -2h 30m.
How do I convert IRST time to BST time?
Add -2h 30m to IRST local time. For example, 9:00 AM in IRST is 6:30 AM in BST.
What time is it in BST right now?
BST uses BST at UTC+01:00. Use the live converter at the top of this page — it updates in real time and already accounts for the -2h 30m offset from IRST.
What is the best time to call BST from IRST?
Call between 11:30 AM and 5:00 PM IRST — that maps to 9:00 AM–2:30 PM BST and keeps both parties inside the working day.
Which is behind, IRST or BST?
IRST is 2 hours 30 minutes behind BST. When it is 12:00 PM in IRST it is 9:30 AM in BST.
Does daylight saving time affect the IRST–BST difference?
Neither zone observes daylight saving time, so the -2h 30m offset between IRST and BST 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 BST?
Not normally. The -2h 30m gap only pushes the date over the previous day.
What is the time difference between IRST and BST?
BST is -2h 30m from IRST.
What timezone is IRST in?
IRST operates on its local timezone.
What timezone is BST in?
BST 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 BST timezone?
Major cities in the BST timezone include London, Birmingham, Manchester, Glasgow, Edinburgh, Cardiff, Belfast, Liverpool.
What is the UTC offset for BST?
British Summer Time (BST) is at UTC+01:00. During daylight saving time, it shifts to BST.
What should I know about the BST timezone?
BST runs from the last Sunday in March to the last Sunday in October. BST is exactly one hour ahead of GMT, the UK's standard time.
When is it midnight in IRST, what time is it in BST?
When it is 12:00 AM (midnight) in IRST (IRST), it is -2h 30m later in BST (BST).
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