What is the time difference between London and Tehran?

Tehran is 3 hours 30 minutes ahead of London when London is on GMT (UTC+0) and Tehran is on IRST (UTC+3:30). When London switches to BST (UTC+1) the gap narrows to 2 hours 30 minutes. If Tehran is on IRDT (UTC+4:30) and London is on GMT, the gap is 4 hours 30 minutes.

Does Tehran observe Daylight Saving Time?

Yes. Iran advances its clocks by one hour in spring, switching from IRST (UTC+3:30) to IRDT (UTC+4:30). Iran and the UK observe DST on different schedules, so the exact offset can take up to four distinct values across the year.

Why is the Tehran offset a half-hour?

Iran chose UTC+3:30 as its standard time to better align solar noon with clock noon across the country. Several countries use non-integer UTC offsets for similar geographic reasons.

What are the best meeting times for London and Tehran?

When London is on GMT, a 09:00–13:30 London window corresponds to 12:30–17:00 in Tehran — a solid mid-day overlap. When London is on BST the overlap shifts slightly. Morning London time generally works well for both cities.

Is this tool accurate for scheduling?

Yes. It uses the IANA timezone database embedded in your browser — the same source used by operating systems and calendar apps worldwide. Accuracy depends on your device clock being synchronized via NTP, which most devices do automatically.

IRST stands for Iran Standard Time. It is UTC+3:30, used across Iran from late September/early October through late March. During summer Iran observes IRDT (Iran Daylight Time), which is UTC+4:30.

Time Difference: London to Tehran

Name: Time Difference: London to Tehran
Availability: InStock
Author: Nham Vu

See the current time in London and Tehran side by side, with the live UTC offset. Iran uses a half-hour offset (UTC+3:30 in winter, UTC+4:30 in summer), so the gap is 3.5 or 2.5 hours depending on DST.

London, United Kingdom

--:--:--

GMT UTC+0

Tehran, Iran

--:--:--

IRST UTC+3:30

Current Offset

+3h 30m

Tehran is 3 hours 30 minutes ahead of London

Meeting Overlap Finder

Business hours (09:00–18:00) highlighted — best overlap shaded

London	Tehran	Status

Convert London Time to Tehran Time

Based on the current offset — updates automatically

London	Tehran

Summary

How it works

Your browser reads the current moment from your device clock.
It converts that moment to Europe/London time using the IANA timezone database built into modern browsers.
The same moment is converted to Asia/Tehran time (IRST UTC+3:30 in winter, IRDT UTC+4:30 in summer).
The UTC offsets of both cities are compared to calculate the exact difference, including the 30-minute fractional component.
All three values — London time, Tehran time, and the offset — refresh every second.
When either city shifts its clocks for DST, the displayed offset adjusts automatically.

Use cases

Scheduling video calls between London and Tehran offices.
Checking if a colleague in Tehran is still at their desk.
Planning UK-Iran travel and arrival time comparisons.
Remote teams coordinating daily standups across the UK and Iran.
Finding overlapping business hours for London-Tehran meetings.
Verifying whether Tehran is currently on IRST or IRDT.
Investors monitoring London and Tehran stock exchange hours.
Students and teachers arranging online lessons between the UK and Iran.

Frequently Asked Questions

Last updated: 2026-06-11 · Reviewed by Nham Vu