UA 6081 then UA 4821 at Houston
Denver → Houston → Amarillo
Timetable, Houston time
10:30UA 6081 from Denver at the gate
09:30UA 4821 to Amarillo leaves the gate
23 h apart on the timetable, overnight
UA 4821 leaves 23 h after UA 6081 arrives on the timetable: more than half a day, so not a connection we count.