San Diego is 8 hours behind Reykjavik
Best overlap: 4:00 PM to 6:00 PM in Reykjavik is 8:00 AM to 10:00 AM in San Diego.
For the smoothest call, aim inside 4:00 PM to 6:00 PM in Reykjavik, i.e. 8:00 AM to 10:00 AM in San Diego. San Diego is 8 hours behind Reykjavik, so common hours are scarce (about 2 hours). Lock the slot, keep it short, and follow up in writing. Daylight saving complicates things slightly: San Diego observes it, Reykjavik doesn't, so the difference flexes by an hour part of the year.