UA 356 then DL 2398 at Atlanta
Chicago O'Hare → Atlanta → New York JFK
Timetable, Atlanta time
17:38UA 356 from Chicago O'Hare at the gate
15:16DL 2398 to New York JFK leaves the gate
21 h 38 apart on the timetable, overnight
DL 2398 leaves 21 h 38 after UA 356 arrives on the timetable: more than half a day, so not a connection we count.