UA 1254 then DL 1697 at Phoenix
Denver → Phoenix → Boston
Timetable, Phoenix time
18:22UA 1254 from Denver at the gate
14:20DL 1697 to Boston leaves the gate
19 h 58 apart on the timetable, overnight
DL 1697 leaves 19 h 58 after UA 1254 arrives on the timetable: more than half a day, so not a connection we count.