DL 977 then UA 8100 at San Francisco
Boston → San Francisco → Vancouver
Timetable, San Francisco time
11:41DL 977 from Boston at the gatealso LY 4578
06:30UA 8100 to Vancouver leaves the gate
18 h 49 apart on the timetable, overnight
UA 8100 leaves 18 h 49 after DL 977 arrives on the timetable: more than half a day, so not a connection we count.