Atlanta is 9.5 hours behind Chennai
Best overlap: 5:30 PM to 6:30 PM in Chennai is 8:00 AM to 9:00 AM in Atlanta.
Aim for 5:30 PM to 6:30 PM Chennai time — that's 8:00 AM to 9:00 AM over in Atlanta. Atlanta is 9.5 hours behind Chennai, so you only get about 1 hour of overlap a day — worth locking in a standing time like 5:30 PM in Chennai (8:00 AM in Atlanta) before it slips. Finally, Atlanta observes daylight saving and Chennai doesn't, so this window shifts by an hour for part of the year — recheck it each spring and autumn.