UA 367 then UA 1665 at San Francisco
Washington → San Francisco → Boston
Timetable, San Francisco time
01:29UA 367 from Washington at the gatealso LH 7530, VA 8388, NZ 9181
23:20UA 1665 to Boston leaves the gatealso VA 8306, NZ 9018
21 h 51 apart on the timetable
UA 1665 leaves 21 h 51 after UA 367 arrives on the timetable: more than half a day, so not a connection we count.