Honolulu is 13 hours behind Helsinki

There is no standard 8-to-6 overlap. Someone joins early or late.

There's no shared 9-to-5 between Helsinki and Honolulu; at 13 hours apart, one city's workday is the other's evening or night. Your best bet is one team taking an early-morning or late-evening call — alternating who stretches keeps it fair over time. Remember that Helsinki shifts for daylight saving and Honolulu doesn't, so recalculate the overlap after each clock change.