UA 4746 then UA 3907 at Houston
Nashville → Houston → Washington
Timetable, Houston time
11:02UA 4746 from Nashville at the gate
07:00UA 3907 to Washington leaves the gate
19 h 58 apart on the timetable, overnight
UA 3907 leaves 19 h 58 after UA 4746 arrives on the timetable: more than half a day, so not a connection we count.