UA 558 then DL 5630 at Boston
Denver → Boston → Charlotte
Timetable, Boston time
13:42UA 558 from Denver at the gate
11:15DL 5630 to Charlotte leaves the gate
21 h 33 apart on the timetable, overnight
DL 5630 leaves 21 h 33 after UA 558 arrives on the timetable: more than half a day, so not a connection we count.