BA 349 then BA 287 at Heathrow
Nice → London → San Francisco
Timetable, London time
21:05BA 349 from Nice at the gate
15:20BA 287 to San Francisco leaves the gate
18 h 15 apart on the timetable, overnight
BA 287 leaves 18 h 15 after BA 349 arrives on the timetable: more than half a day, so not a connection we count.