UA 640 then WN 988 at Denver
Vancouver → Denver → Buffalo
Timetable, Denver time
12:20UA 640 from Vancouver at the gate
11:50WN 988 to Buffalo leaves the gate
23 h 30 apart on the timetable, overnight
WN 988 leaves 23 h 30 after UA 640 arrives on the timetable: more than half a day, so not a connection we count.