BA 391 then BA 227 at Heathrow
Brussels → London → Atlanta
Timetable, London time
16:20BA 391 from Brussels at the gate
15:35BA 227 to Atlanta leaves the gate
23 h 15 apart on the timetable, overnight
BA 227 leaves 23 h 15 after BA 391 arrives on the timetable: more than half a day, so not a connection we count.