BA 341 then BA 746 at Heathrow
Nice → London → Geneva
Timetable, London time
13:30BA 341 from Nice at the gate
10:30BA 746 to Geneva leaves the gate
21 h apart on the timetable, overnight
BA 746 leaves 21 h after BA 341 arrives on the timetable: more than half a day, so not a connection we count.