Tukuk-OS🕒 Tehran to London time
| Tehran on 2026-11-06 | 12:00 (GMT+3:30) |
| London at that instant | 08:30 the same day (GMT+0) |
| Difference on this date | 3 h 30 min (2026-10-25 to 2026-12-31) |
| 2026-01-01 to 2026-03-28 | 3 h 30 min |
| 2026-03-29 to 2026-10-24 | 2 h 30 min |
| 2026-10-25 to 2026-12-31 | 3 h 30 min |
| Next clock change, Tehran | none in the next 200 days |
| Next clock change, London | Sunday 28 March 2027 at 01:00 UTC |
| 09:00 in Tehran is | 05:30 in London |
| 12:00 in Tehran is | 08:30 in London |
| 18:00 in Tehran is | 14:30 in London |
| Shared 09:00–17:00 working window | 13:00–17:00 in Tehran, 09:30–13:30 in London |
ℹ️ What this tool does & how it works
On 2026-11-06 the two clocks are apart by 3 h 30 min, with Tehran ahead. Tehran runs on GMT+3:30 and London on GMT+0. Across 2026 the difference runs: 2026-01-01 → 2026-03-28: 3 h 30 min; 2026-03-29 → 2026-10-24: 2 h 30 min; 2026-10-25 → 2026-12-31: 3 h 30 min. Pick any date and time below and the page reworks the whole table from your own device.
Why the gap between Tehran and London changes during 2026
Two places drift apart and come back again whenever one of them changes its clocks and the other does not — which is the situation between a place that observes daylight saving and one that does not, or between two that pick different Sundays for it. In 2026 the difference between Tehran and London runs: 2026-01-01 → 2026-03-28: 3 h 30 min; 2026-03-29 → 2026-10-24: 2 h 30 min; 2026-10-25 → 2026-12-31: 3 h 30 min. A meeting arranged in the middle of one of those runs is safe; one arranged across a boundary is the classic four-hours-late call, so the table names the boundaries instead of leaving you to remember them.
The clock changes, and who decides them
Tehran uses the zone Asia/Tehran, which does not change its clocks. London uses the zone Europe/London, and its next change after 2026-11-06 is Sunday 28 March 2027 at 01:00 UTC. Neither figure is a physical fact: an offset is legislation, and the same fifteen degrees of longitude can sit under three zones because a border runs through it. That is why this page reads its offsets out of the time-zone database built into your own browser instead of hardcoding a table of abbreviations — it is the database your operating system already keeps current, and it is what puts Tehran and London in the right relation even when a government moves a date at short notice. A device whose database predates the last change gets the old answer, which is the one caveat worth knowing.
What it is actually like to work across the two
Both places are inside their own 09:00–17:00 on 4 hours of the day: 13:00–17:00 in Tehran, 09:30–13:30 in London — outside those hours somebody is starting early, finishing late or taking the call at midnight. The two clock rules here are not unique to these two places: 13 other cities in our dataset keep the same clock as one of them, including Isfahan, Shiraz, Tabriz, Manchester, Edinburgh, so looking any of those up against the city on the other side of the pair gives this page’s answers. The arithmetic is the three lines the page runs in front of you: read each zone’s offset for the date you picked, subtract, and let the modulo handle the dateline.