BA 294 then BA 590 at Heathrow
Chicago → London → Venezia
Timetable, London time
06:55BA 294 from Chicago at the gate
06:40BA 590 to Venezia leaves the gate
23 h 45 apart on the timetable, overnight
BA 590 leaves 23 h 45 after BA 294 arrives on the timetable: more than half a day, so not a connection we count.