DL 1780 then DL 1599 at Boston
Atlanta → Boston → Washington National
Timetable, Boston time
23:27DL 1780 from Atlanta at the gate
20:05DL 1599 to Washington National leaves the gate
20 h 38 apart on the timetable, overnight
DL 1599 leaves 20 h 38 after DL 1780 arrives on the timetable: more than half a day, so not a connection we count.