WN 209 then UA 2013 at Denver
St Louis → Denver → Seattle
Timetable, Denver time
18:50WN 209 from St Louis at the gate
15:55UA 2013 to Seattle leaves the gate
21 h 05 apart on the timetable, overnight
UA 2013 leaves 21 h 05 after WN 209 arrives on the timetable: more than half a day, so not a connection we count.