DL 5697 then DL 1599 at Boston
Richmond → Boston → Washington National
Timetable, Boston time
08:00DL 5697 from Richmond at the gate
20:05DL 1599 to Washington National leaves the gate
12 h 05 apart on the timetable
DL 1599 leaves 12 h 05 after DL 5697 arrives on the timetable: more than half a day, so not a connection we count.