GQ 681 then JU 533 at Athens
Sofia → Athens → Belgrade
Timetable, Athens time
21:55GQ 681 from Sofia at the gate
15:50JU 533 to Belgrade leaves the gate
17 h 55 apart on the timetable, overnight
JU 533 leaves 17 h 55 after GQ 681 arrives on the timetable: more than half a day, so not a connection we count.