Copenhagen is 1 hour behind Istanbul
Best overlap: 9:00 AM to 6:00 PM in Istanbul is 8:00 AM to 5:00 PM in Copenhagen.
Your window to reach both cities is 9:00 AM to 6:00 PM in Istanbul, which converts to 8:00 AM to 5:00 PM in Copenhagen. A 9-hour overlap gives you real choice here — early or late in the window both work comfortably. One seasonal catch: Copenhagen springs forward and falls back, but Istanbul doesn't, so the gap changes by an hour for several months of the year.