DL 4020 then DL 438 at Seattle
Vancouver → Seattle → Boston
Timetable, Seattle time
12:37DL 4020 from Vancouver at the gate
11:45DL 438 to Boston leaves the gate
23 h 08 apart on the timetable, overnight
DL 438 leaves 23 h 08 after DL 4020 arrives on the timetable: more than half a day, so not a connection we count.