San Diego is 9 hours behind Copenhagen
Best overlap: 5:00 PM to 6:00 PM in Copenhagen is 8:00 AM to 9:00 AM in San Diego.
Shoot for 5:00 PM to 6:00 PM in Copenhagen; your San Diego colleagues will see that as 8:00 AM to 9:00 AM. Overlap is at a premium — roughly 1 hour — so claim 5:00 PM in Copenhagen (8:00 AM in San Diego) for recurring calls and keep them on time.