Moscow is 1 hour ahead of Oslo
Best overlap: 8:00 AM to 5:00 PM in Oslo is 9:00 AM to 6:00 PM in Moscow.
If you set up a recurring sync, 8:00 AM to 5:00 PM in Oslo (9:00 AM to 6:00 PM in Moscow) is the natural home for it. Because you share 9 hours of the workday, there's no need to compromise; book the time that suits the meeting, not the map. Remember that Oslo shifts for daylight saving and Moscow doesn't, so recalculate the overlap after each clock change.