BA 238 then BA 352 at Heathrow
Boston → London → Nice
Timetable, London time
19:00BA 238 from Boston at the gate
18:05BA 352 to Nice leaves the gate
23 h 05 apart on the timetable, overnight
BA 352 leaves 23 h 05 after BA 238 arrives on the timetable: more than half a day, so not a connection we count.