BA 391 then BA 287 at Heathrow
Brussels → London → San Francisco
Timetable, London time
16:15BA 391 from Brussels at the gate
15:20BA 287 to San Francisco leaves the gate
23 h 05 apart on the timetable, overnight
BA 287 leaves 23 h 05 after BA 391 arrives on the timetable: more than half a day, so not a connection we count.