BA 36 then BA 746 at Heathrow
Chennai → London → Geneva
Timetable, London time
13:35BA 36 from Chennai at the gate
10:30BA 746 to Geneva leaves the gate
20 h 55 apart on the timetable, overnight
BA 746 leaves 20 h 55 after BA 36 arrives on the timetable: more than half a day, so not a connection we count.