UA 411 then DL 2597 at Atlanta
Chicago O'Hare → Atlanta → Montréal
Timetable, Atlanta time
09:53UA 411 from Chicago O'Hare at the gate
09:00DL 2597 to Montréal leaves the gate
23 h 07 apart on the timetable, overnight
DL 2597 leaves 23 h 07 after UA 411 arrives on the timetable: more than half a day, so not a connection we count.