Warsaw 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 Warsaw.
Keep meetings inside 9:00 AM to 6:00 PM in Istanbul — that maps to 8:00 AM to 5:00 PM in Warsaw. Warsaw is 1 hour behind Istanbul, but the generous 9-hour window means both teams can meet well within their normal day. These times hold for most of the year, but Warsaw's daylight saving (which Istanbul doesn't use) shifts them by an hour twice annually.