BA 631 then BA 293 at Heathrow
Athens → London → Washington
Timetable, London time
16:30BA 631 from Athens at the gate
16:25BA 293 to Washington leaves the gate
23 h 55 apart on the timetable, overnight
BA 293 leaves 23 h 55 after BA 631 arrives on the timetable: more than half a day, so not a connection we count.