KL 618 then U2 7927 at Schiphol
Boston → Amsterdam → Prague
Timetable, Amsterdam time
09:45KL 618 from Boston at the gate
07:15U2 7927 to Prague leaves the gate
21 h 30 apart on the timetable, overnight
U2 7927 leaves 21 h 30 after KL 618 arrives on the timetable: more than half a day, so not a connection we count.