UA 3913 then AA 2504 at Houston
Denver → Houston → Chicago
Timetable, Houston time
21:22UA 3913 from Denver at the gate
11:26AA 2504 to Chicago leaves the gate
14 h 04 apart on the timetable, overnight
AA 2504 leaves 14 h 04 after UA 3913 arrives on the timetable: more than half a day, so not a connection we count.