DL 850 then DL 543 at Atlanta
Washington National → Atlanta → St Louis
Timetable, Atlanta time
20:29DL 850 from Washington National at the gate
15:45DL 543 to St Louis leaves the gate
19 h 16 apart on the timetable, overnight
DL 543 leaves 19 h 16 after DL 850 arrives on the timetable: more than half a day, so not a connection we count.