DL 706 then DL 1554 at Atlanta
Denver → Atlanta → Washington
Timetable, Atlanta time
18:01DL 706 from Denver at the gate
15:27DL 1554 to Washington leaves the gate
21 h 26 apart on the timetable, overnight
DL 1554 leaves 21 h 26 after DL 706 arrives on the timetable: more than half a day, so not a connection we count.