UA 643 then AV 2354 at San Francisco
Las Vegas → San Francisco → Denver
Timetable, San Francisco time
07:44UA 643 from Las Vegas at the gatealso AC 5211, NH 7315, VA 8122, NZ 9237
05:00AV 2354 to Denver leaves the gate
21 h 16 apart on the timetable, overnight
AV 2354 leaves 21 h 16 after UA 643 arrives on the timetable: more than half a day, so not a connection we count.