Reykjavik is 6 hours ahead of Dallas
Best overlap: 8:00 AM to 12:00 PM in Dallas is 2:00 PM to 6:00 PM in Reykjavik.
Keep meetings inside 8:00 AM to 12:00 PM in Dallas — that maps to 2:00 PM to 6:00 PM in Reykjavik. With 4 hours of overlap, 8:00 AM in Dallas (2:00 PM in Reykjavik) is a comfortable, repeatable slot for both sides. Because Dallas and Reykjavik don't both observe daylight saving, plan to re-check the overlap around March and November.