UA 644 then DL 3876 at Denver
Dallas-Fort Worth → Denver → Austin
Timetable, Denver time
10:14UA 644 from Dallas-Fort Worth at the gate
09:42DL 3876 to Austin leaves the gate
23 h 28 apart on the timetable, overnight
DL 3876 leaves 23 h 28 after UA 644 arrives on the timetable: more than half a day, so not a connection we count.