F9 4567 then UA 2123 at Denver
St Louis → Denver → San Francisco
Timetable, Denver time
21:30F9 4567 from St Louis at the gate
21:18UA 2123 to San Francisco leaves the gate
23 h 48 apart on the timetable, overnight
UA 2123 leaves 23 h 48 after F9 4567 arrives on the timetable: more than half a day, so not a connection we count.