A3 712 then QR 3683 at Barcelona
Athens → Barcelona → Santander
Timetable, Barcelona time
18:45A3 712 from Athens at the gate
16:05QR 3683 to Santander leaves the gate
21 h 20 apart on the timetable, overnight
QR 3683 leaves 21 h 20 after A3 712 arrives on the timetable: more than half a day, so not a connection we count.