Daylight saving time
Istanbul (Türkiye) does not change clocks: UTC+3 all year. London (United Kingdom) observes daylight saving time from the last Sunday of March to the last Sunday of October: UTC+0 in January, UTC+1 in July.
Türkiye has stayed on UTC+3 permanently since 2016 and does not change clocks. London uses GMT (UTC+0) in winter and British Summer Time (BST, UTC+1) in summer.
Best time for a call
If both sides work 9:00–18:00 local time, the shared window is 12:00–18:00 in Istanbul = 09:00–15:00 in London (6 hours) in January and 11:00–18:00 in Istanbul = 09:00–16:00 in London (7 hours) in July. Put recurring calls in this window and state the time with the city name (for example “14:00 Istanbul time”) to avoid confusion. How to schedule a meeting across time zones.
How to read the chart
The left column is the local time in Istanbul, the other columns show the same moment in London in January and in July. “+1 day” means it is already the next calendar day in London, “−1 day” — still the previous one. Rows outside 9:00–18:00 are dimmed. The converter above works the other way too: press “Swap” to enter a time in London.