UA 6088 then DL 2709 at Houston
Denver → Houston → Atlanta
Timetable, Houston time
10:45UA 6088 from Denver at the gate
08:05DL 2709 to Atlanta leaves the gate
21 h 20 apart on the timetable, overnight
DL 2709 leaves 21 h 20 after UA 6088 arrives on the timetable: more than half a day, so not a connection we count.