UA 323 then DL 3876 at Denver
Philadelphia → Denver → Austin
Timetable, Denver time
10:05UA 323 from Philadelphia at the gate
09:42DL 3876 to Austin leaves the gate
23 h 37 apart on the timetable, overnight
DL 3876 leaves 23 h 37 after UA 323 arrives on the timetable: more than half a day, so not a connection we count.