BA 753 then DL 59 at Heathrow
Geneva → London → Boston
Timetable, London time
10:00BA 753 from Geneva at the gate
09:40DL 59 to Boston leaves the gate
23 h 40 apart on the timetable, overnight
DL 59 leaves 23 h 40 after BA 753 arrives on the timetable: more than half a day, so not a connection we count.