A3 877 then GQ 344 at Athens
Budapest → Athens → Santorini
Timetable, Athens time
19:20A3 877 from Budapest at the gate
17:15GQ 344 to Santorini leaves the gate
21 h 55 apart on the timetable, overnight
GQ 344 leaves 21 h 55 after A3 877 arrives on the timetable: more than half a day, so not a connection we count.