DL 360 then DL 543 at Atlanta
Washington National → Atlanta → St Louis
Timetable, Atlanta time
17:55DL 360 from Washington National at the gate
15:45DL 543 to St Louis leaves the gate
21 h 50 apart on the timetable, overnight
DL 543 leaves 21 h 50 after DL 360 arrives on the timetable: more than half a day, so not a connection we count.