DL 499 then DL 5665 at Boston
Denver → Boston → Richmond
Timetable, Boston time
17:27DL 499 from Denver at the gate
15:20DL 5665 to Richmond leaves the gate
21 h 53 apart on the timetable, overnight
DL 5665 leaves 21 h 53 after DL 499 arrives on the timetable: more than half a day, so not a connection we count.