BA 873 then AC 865 at Heathrow
Krakow → London → Montréal
Timetable, London time
18:05BA 873 from Krakow at the gate
13:00AC 865 to Montréal leaves the gate
18 h 55 apart on the timetable, overnight
AC 865 leaves 18 h 55 after BA 873 arrives on the timetable: more than half a day, so not a connection we count.