Reykjavik is 5 hours ahead of Atlanta
Best overlap: 8:00 AM to 1:00 PM in Atlanta is 1:00 PM to 6:00 PM in Reykjavik.
For the smoothest call, aim inside 8:00 AM to 1:00 PM in Atlanta, i.e. 1:00 PM to 6:00 PM in Reykjavik. Reykjavik is 5 hours ahead of Atlanta, so the practical overlap is about 5 hours — generous enough for meetings, tight enough to be worth booking ahead. For part of the year the maths changes: Atlanta observes daylight saving, Reykjavik does not, shifting the overlap by an hour.