Helsinki is 2 hours ahead of Reykjavik
Best overlap: 8:00 AM to 4:00 PM in Reykjavik is 10:00 AM to 6:00 PM in Helsinki.
If you set up a recurring sync, 8:00 AM to 4:00 PM in Reykjavik (10:00 AM to 6:00 PM in Helsinki) is the natural home for it. Because you share 8 hours of the workday, there's no need to compromise; book the time that suits the meeting, not the map. Finally, Helsinki observes daylight saving and Reykjavik doesn't, so this window shifts by an hour for part of the year — recheck it each spring and autumn.