UA 584 then DL 2709 at Houston
Philadelphia → Houston → Atlanta
Timetable, Houston time
10:48UA 584 from Philadelphia at the gate
08:05DL 2709 to Atlanta leaves the gate
21 h 17 apart on the timetable, overnight
DL 2709 leaves 21 h 17 after UA 584 arrives on the timetable: more than half a day, so not a connection we count.