UA 5885 then DL 3876 at Denver
Rapid City → Denver → Austin
Timetable, Denver time
12:04UA 5885 from Rapid City at the gate
09:42DL 3876 to Austin leaves the gate
21 h 38 apart on the timetable, overnight
DL 3876 leaves 21 h 38 after UA 5885 arrives on the timetable: more than half a day, so not a connection we count.