UA 503 then DL 5704 at Boston
Newark → Boston → Washington National
Timetable, Boston time
09:17UA 503 from Newark at the gate
21:45DL 5704 to Washington National leaves the gate
12 h 28 apart on the timetable
DL 5704 leaves 12 h 28 after UA 503 arrives on the timetable: more than half a day, so not a connection we count.