AA 3300 then UA 3872 at O'Hare
Denver → Chicago → LCQ
Timetable, Chicago time
11:45AA 3300 from Denver at the gate
00:31UA 3872 to LCQ leaves the gate
12 h 46 apart on the timetable, overnight
UA 3872 leaves 12 h 46 after AA 3300 arrives on the timetable: more than half a day, so not a connection we count.