Vienna 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 Vienna.

Keep meetings inside 9:30 AM to 6:30 PM in Tehran — that maps to 8:00 AM to 5:00 PM in Vienna. Vienna is 1.5 hours behind Tehran, but you still share a generous 9 hours of overlap, so scheduling is easy and there's room to move a meeting when you need to. These times hold for most of the year, but Vienna's daylight saving (which Tehran doesn't use) shifts them by an hour twice annually.