AA 873 then UA 2050 at O'Hare
Atlanta → Chicago → Denver
Timetable, Chicago time
13:18AA 873 from Atlanta at the gate
13:00UA 2050 to Denver leaves the gate
23 h 42 apart on the timetable, overnight
UA 2050 leaves 23 h 42 after AA 873 arrives on the timetable: more than half a day, so not a connection we count.