AA 2921 then CA 3174 at O'Hare
Buffalo → Chicago → Guangzhou
Timetable, Chicago time
19:00AA 2921 from Buffalo at the gate
13:40CA 3174 to Guangzhou leaves the gate
18 h 40 apart on the timetable, overnight
CA 3174 leaves 18 h 40 after AA 2921 arrives on the timetable: more than half a day, so not a connection we count.