OZ 521 then KL 9936 at Heathrow
Seoul → London → Amsterdam
Timetable, London time
15:35OZ 521 from Seoul at the gate
12:13KL 9936 to Amsterdam leaves the gate
20 h 38 apart on the timetable, overnight
KL 9936 leaves 20 h 38 after OZ 521 arrives on the timetable: more than half a day, so not a connection we count.