UA 5935 then UA 1639 at Denver
Salt Lake City → Denver → St Louis
Timetable, Denver time
20:03UA 5935 from Salt Lake City at the gate
13:55UA 1639 to St Louis leaves the gate
17 h 52 apart on the timetable, overnight
UA 1639 leaves 17 h 52 after UA 5935 arrives on the timetable: more than half a day, so not a connection we count.