UA 3913 then UA 1998 at Houston
Denver → Houston → Cincinnati
Timetable, Houston time
21:22UA 3913 from Denver at the gate
12:20UA 1998 to Cincinnati leaves the gate
14 h 58 apart on the timetable, overnight
UA 1998 leaves 14 h 58 after UA 3913 arrives on the timetable: more than half a day, so not a connection we count.