Portland is 16 hours behind Hong Kong
Best overlap: 8:00 AM to 10:00 AM in Hong Kong is 4:00 PM to 6:00 PM in Portland.
8:00 AM to 10:00 AM in Hong Kong is when Portland is also working, at 4:00 PM to 6:00 PM their time. The overlap is tight at roughly 2 hours, so protect it: 8:00 AM in Hong Kong / 4:00 PM in Portland is your safest recurring slot. The overlap spans the date line; in practical terms, Portland is on the previous day compared to Hong Kong. Because only Portland changes its clocks, the overlap above isn't fixed; expect a one-hour shift when Portland enters or leaves daylight saving.