BA 851 then DL 59 at Heathrow
Warsaw → London → Boston
Timetable, London time
09:50BA 851 from Warsaw at the gate
09:40DL 59 to Boston leaves the gate
23 h 50 apart on the timetable, overnight
DL 59 leaves 23 h 50 after BA 851 arrives on the timetable: more than half a day, so not a connection we count.