UA 377 then CV 12 at O'Hare
Denver → Chicago → Luxembourg
Timetable, Chicago time
23:59UA 377 from Denver at the gate
21:56CV 12 to Luxembourg leaves the gate
21 h 57 apart on the timetable, overnight
CV 12 leaves 21 h 57 after UA 377 arrives on the timetable: more than half a day, so not a connection we count.