SQ 1539 then UA 785 at San Francisco
Boston → San Francisco → Washington
Timetable, San Francisco time
09:40SQ 1539 from Boston at the gate
06:15UA 785 to Washington leaves the gatealso AZ 4408, NZ 9160
20 h 35 apart on the timetable, overnight
UA 785 leaves 20 h 35 after SQ 1539 arrives on the timetable: more than half a day, so not a connection we count.