Hong Kong is 5 hours ahead of Cairo
Best overlap: 8:00 AM to 1:00 PM in Cairo is 1:00 PM to 6:00 PM in Hong Kong.
Cairo and Hong Kong overlap from 8:00 AM to 1:00 PM (Cairo) to the equivalent 1:00 PM to 6:00 PM in Hong Kong — that's your meeting window. The shared window is roughly 5 hours; treat its midpoint as the default and you'll keep both teams happy. The difference isn't constant year-round: Cairo adjusts for daylight saving while Hong Kong holds steady.