Oslo is 1.5 hours behind Tehran

Best overlap: 9:30 AM to 6:30 PM in Tehran is 8:00 AM to 5:00 PM in Oslo.

For a call that suits both sides, look at 9:30 AM to 6:30 PM in Tehran / 8:00 AM to 5:00 PM in Oslo. Because you share 9 hours of the workday, there's no need to compromise; book the time that suits the meeting, not the map. These times hold for most of the year, but Oslo's daylight saving (which Tehran doesn't use) shifts them by an hour twice annually.