UA 3913 then UA 654 at Houston
Denver → Houston → Washington National
Timetable, Houston time
21:22UA 3913 from Denver at the gate
12:07UA 654 to Washington National leaves the gate
14 h 45 apart on the timetable, overnight
UA 654 leaves 14 h 45 after UA 3913 arrives on the timetable: more than half a day, so not a connection we count.