Philadelphia is 7 hours behind Nairobi
Best overlap: 3:00 PM to 6:00 PM in Nairobi is 8:00 AM to 11:00 AM in Philadelphia.
Target 3:00 PM to 6:00 PM in Nairobi, which lands at 8:00 AM to 11:00 AM for the Philadelphia side. Since Philadelphia is 7 hours behind Nairobi, the workdays overlap by around 3 hours; 3:00 PM in Nairobi (8:00 AM in Philadelphia) makes a reliable recurring slot. Note that Philadelphia follows daylight saving while Nairobi stays put, so the times above drift by an hour seasonally.