Nairobi is 2.5 hours behind Chennai
Best overlap: 10:30 AM to 6:30 PM in Chennai is 8:00 AM to 4:00 PM in Nairobi.
The overlap falls at 10:30 AM to 6:30 PM in Chennai, or 8:00 AM to 4:00 PM if you're in Nairobi. The 2.5-hour gap barely gets in the way — you've got 8 hours of overlap, so pick whatever time fits the agenda.