UA 3876 then UA 2000 at O'Hare
Miami → Chicago → St Louis
Timetable, Chicago time
14:49UA 3876 from Miami at the gate
14:12UA 2000 to St Louis leaves the gate
23 h 23 apart on the timetable, overnight
UA 2000 leaves 23 h 23 after UA 3876 arrives on the timetable: more than half a day, so not a connection we count.