Oslo 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 Oslo.
If you set up a recurring sync, 9:00 AM to 6:00 PM in Istanbul (8:00 AM to 5:00 PM in Oslo) is the natural home for it. Oslo is 1 hour behind Istanbul, but the generous 9-hour window means both teams can meet well within their normal day. Remember that Oslo shifts for daylight saving and Istanbul doesn't, so recalculate the overlap after each clock change.