Dallas is 8 hours behind Istanbul
Best overlap: 4:00 PM to 6:00 PM in Istanbul is 8:00 AM to 10:00 AM in Dallas.
If you set up a recurring sync, 4:00 PM to 6:00 PM in Istanbul (8:00 AM to 10:00 AM in Dallas) is the natural home for it. With overlap this short — around 2 hours — a recurring slot at 4:00 PM in Istanbul (8:00 AM in Dallas) is worth its weight in gold. Because Dallas and Istanbul don't both observe daylight saving, plan to re-check the overlap around March and November.