UA 558 then DL 1439 at Boston
Denver → Boston → Tampa
Timetable, Boston time
13:42UA 558 from Denver at the gate
13:20DL 1439 to Tampa leaves the gate
23 h 38 apart on the timetable, overnight
DL 1439 leaves 23 h 38 after UA 558 arrives on the timetable: more than half a day, so not a connection we count.