London to Tehran
+2h 30mLondon
BSTSOURCETehran
IRSTGreen rows indicate typical business hours (9 AM - 5 PM)
BST and IRST on the World Map
The map below highlights the BST (Greenwich Mean Time) and IRST (Iran Standard Time) timezone regions across the globe.
GMT – Greenwich Mean Time
UTC+00:00Greenwich Mean Time (GMT) is the mean solar time at the Royal Observatory in Greenwich, London. It is the same as UTC+00:00.
- •GMT is based on the Prime Meridian (0° longitude) passing through Greenwich, London.
- •The Royal Observatory in Greenwich has been the reference point for GMT since 1884.
- •GMT and UTC are often used interchangeably, but UTC is based on atomic clocks.
- •Iceland uses GMT year-round and never observes daylight saving time.
- •The UK switches from GMT to BST (British Summer Time) in late March each year.
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 London
WikipediaLondon, where Greenwich Mean Time (GMT) originates, is the world's leading financial center alongside New York. The city bridges European and American business hours.
Big Ben is actually the name of the bell inside the Elizabeth Tower, not the tower itself.
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).
London vs Tehran: Offsets, DST and Best Call Times
London runs on British Summer Time (BST) at UTC+01:00, currently observing daylight saving time. Tehran runs on Iran Standard Time (IRST) at UTC+03:30. That puts London 2 hours 30 minutes ahead of Tehran — a difference of +2h 30m at the current offsets.
In practice, when it is 9:00 AM in London it is 11:30 AM in Tehran. Midnight in London is 2:30 AM in Tehran.London observes daylight saving time while Tehran does not, so the gap narrows or widens by an hour part of the year.
London to Tehran time conversion table
| London (BST) | Tehran (IRST) | Day |
|---|---|---|
| 12:00 AM | 2:30 AM | same day |
| 6:00 AM | 8:30 AM | same day |
| 7:00 AM | 9:30 AM | same day |
| 8:00 AM | 10:30 AM | same day |
| 9:00 AM | 11:30 AM | same day |
| 12:00 PM | 2:30 PM | same day |
| 3:00 PM | 5:30 PM | same day |
| 5:00 PM | 7:30 PM | same day |
| 6:00 PM | 8:30 PM | same day |
| 9:00 PM | 11:30 PM | same day |
Why people convert London to Tehran time
- Scheduling a call from London to Tehran: a 10:00 AM start in London lands at 12:30 PM in Tehran, so you can confirm the slot without doing the arithmetic yourself.
- Finding shared working hours: both London and Tehran are inside the 9-to-5 working day between 9:00 AM and 2:30 PM BST time (11:30 AM–5:00 PM IRST). That is roughly 5 hours 30 minutes of usable overlap.
- Booking travel or deliveries: tracking Tehran local time against London keeps pickup windows and arrival estimates honest across the +2h 30m offset.
- Always state the zone abbreviation, not just the hour. "3:00 PM BST" is unambiguous; "3 PM" across a +2h 30m gap is not.
- Block 9:00 AM–2:30 PM BST as the recurring meeting window if you work primarily from London and need Tehran colleagues present.
- London: Clocks fall back on Sun, Oct 25, 2026. Re-check this page after that date because the offset changes and so does the +2h 30m gap.
About GMT (Greenwich Mean Time)
Greenwich Mean Time (GMT) is the clock time at the Royal Observatory in Greenwich, London, which sits on the Prime Meridian (0° longitude). GMT serves as the reference point from which all other time zones are calculated. The United Kingdom uses GMT during winter months and switches to British Summer Time (BST, UTC+01:00) from late March to late October. Several West African nations use GMT year-round. GMT is often used interchangeably with UTC (Coordinated Universal Time), although technically they are different – UTC is based on atomic clocks while GMT is based on Earth's rotation.
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 London and Tehran
Both London and Tehran sit inside the 9 AM – 5 PM working day between 9:00 AM–2:30 PM BST, which is 11:30 AM–5:00 PM IRST. That gives roughly 5 hours and 30 minutes of shared time — the safest window for a live call or meeting.
Business hours overlap
London and Tehran share 5 hours of working-hours overlap (9:00 AM–2:30 PM BST), so scheduling a live meeting is straightforward.
London is 2 hours 30 minutes ahead of Tehran (BST UTC+01:00 → IRST UTC+03:30). The shared working window is 9:00 AM–2:30 PM BST. Remember to re-check around daylight-saving transitions.
🕐 Daylight Saving Time Info
London
☀ Currently in DST
Standard: UTC+00:00 · DST: UTC+01:00
Clocks fall back on Sun, Oct 25, 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 London and Tehran?
London (BST, UTC+01:00) is 2 hours 30 minutes ahead of Tehran (IRST, UTC+03:30). The gap is currently +2h 30m.
How do I convert London time to Tehran time?
Add +2h 30m to London local time. For example, 9:00 AM in London is 11:30 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 +2h 30m offset from London.
What is the best time to call Tehran from London?
Call between 9:00 AM and 2:30 PM BST — that maps to 11:30 AM–5:00 PM IRST and keeps both parties inside the working day.
Which is ahead, London or Tehran?
London is 2 hours 30 minutes ahead of Tehran. When it is 12:00 PM in London it is 2:30 PM in Tehran.
Do London and Tehran use different time zones?
London (UK) uses BST at UTC+01:00, while Tehran (Iran) uses IRST at UTC+03:30. The IANA identifiers are Europe/London and Asia/Tehran.
Does daylight saving time affect the London–Tehran difference?
Yes at the moment: London is on daylight saving time and Tehran is not, so the +2h 30m gap shifts by an hour when exactly one of them changes clocks.
Which other cities share London's time zone?
BST also covers London, Dublin, Lisbon, Accra, Reykjavik, Edinburgh, Casablanca, Dakar and 5 more.
Which countries use BST, London's zone?
BST is used in United Kingdom, Ireland, Iceland, Portugal (mainland), Ghana, Senegal, Mali, Mauritania and 7 more.
Is there a day difference between London and Tehran?
Not normally. The +2h 30m gap only pushes the date over for late-evening times.
What is the time difference between London and Tehran?
Tehran is +2h 30m from London.
What timezone is London in?
London, where Greenwich Mean Time (GMT) originates, is the world's leading financial center alongside New York. The city bridges European and American business hours.
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 London?
Standard business hours in London are 9:00 AM - 5:00 PM GMT.
What are the business hours in Tehran?
Standard business hours in Tehran are 8:00 AM - 4:00 PM IRST.
What is the best time to schedule a call between London and Tehran?
The best overlap for a call is when both cities are in business hours. London works 9:00 AM - 5:00 PM GMT and Tehran works 8:00 AM - 4:00 PM IRST (+2h 30m difference). Try scheduling during the overlapping window for maximum convenience.
What currencies are used in London and Tehran?
London uses GBP (£) while Tehran uses IRR (﷼). Check current exchange rates when planning travel or business between these cities.
How do London and Tehran compare in size?
London has a population of approximately 8.8 million (metro: 14.8 million), while Tehran has approximately 9.4 million (metro: 16.8 million).
What are the major landmarks in London and Tehran?
London is known for Big Ben, Tower Bridge, Buckingham Palace. Tehran is famous for Azadi Tower, Golestan Palace, Grand Bazaar.
Do London and Tehran have stock exchanges?
Yes. London has the LSE (London Stock Exchange) and Tehran has the TSE (Tehran Stock Exchange). The +2h 30m time difference affects trading hour overlaps between these exchanges.
Which countries use GMT (Greenwich Mean Time)?
GMT is used in United Kingdom, Ireland, Iceland, Portugal (mainland), Ghana, Senegal, and 9 more countries.
Does GMT observe daylight saving time?
Yes, GMT switches to BST during summer months.
What are some interesting facts about GMT?
GMT is based on the Prime Meridian (0° longitude) passing through Greenwich, London. The Royal Observatory in Greenwich has been the reference point for GMT since 1884.
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 London, what time is it in Tehran?
When it is 12:00 AM (midnight) in London (GMT), it is +2h 30m later in Tehran (IRST).
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