Time Difference Between Istanbul and London

Turkey no longer changes its clocks. Istanbul stays on UTC+3 while London moves, so the gap is two hours during British Summer Time and three hours while London is on standard time. Summer time runs from the last Sunday of March to the last Sunday of October. In that stretch, 9 AM in London is 11 AM in Istanbul and 5 PM in London is 7 PM there. In winter, 9 AM London is noon in Istanbul and 5 PM London is 8 PM. The winter evening is the one Istanbul resents as a weekly habit. The summer numbers are an ordinary overlap.

Because only London moves, a recurring invite created in London time holds the London hour and pushes Istanbul an hour later when the clocks go back on the last Sunday of October. The same invite brings Istanbul an hour earlier on the last Sunday of March. Istanbul cannot 'spring forward' to meet you. If the hard stop is an Istanbul evening, anchor the event to Istanbul and let London be the side that reads a different hour twice a year. Friday midday can also run thin in Istanbul, more in government offices and smaller firms than on a trading floor. Do not assume the whole city stops. Do not assume it doesn't, either, if your counterparty is a public office.

The nonstop is about four hours and several airlines fly it all day, so the question is which departure, not whether the route exists. Two or three hours eastbound is a short night. Most people work the next morning. Westbound to London barely registers. Istanbul is also the connection that replaced a lot of other routings, so plenty of travelers meet this clock as a layover at a bad local hour with another flight still ahead. If Istanbul is the destination, the arrival evening is for sleep. If it is the connection, do not schedule a call during the layover.