BA 170 then BA 632 at Heathrow
Pittsburgh → London → Athens
Timetable, London time
09:40BA 170 from Pittsburgh at the gate
09:30BA 632 to Athens leaves the gate
23 h 50 apart on the timetable, overnight
BA 632 leaves 23 h 50 after BA 170 arrives on the timetable: more than half a day, so not a connection we count.