Reykjavik is 1 hour behind Copenhagen
Best overlap: 9:00 AM to 6:00 PM in Copenhagen is 8:00 AM to 5:00 PM in Reykjavik.
The best time to meet is 9:00 AM to 6:00 PM in Copenhagen, which is 8:00 AM to 5:00 PM in Reykjavik. 9 hours of shared hours is more than enough — slot meetings wherever they're most convenient for the people involved. One seasonal catch: Copenhagen springs forward and falls back, but Reykjavik doesn't, so the gap changes by an hour for several months of the year.