UA 2348 then WN 581 at Denver
Boston → Denver → Nashville
Timetable, Denver time
12:08UA 2348 from Boston at the gate
07:55WN 581 to Nashville leaves the gate
19 h 47 apart on the timetable, overnight
WN 581 leaves 19 h 47 after UA 2348 arrives on the timetable: more than half a day, so not a connection we count.