AA 9909 then UA 779 at Denver
Los Angeles → Denver → Boston
Timetable, Denver time
16:45AA 9909 from Los Angeles at the gate
16:01UA 779 to Boston leaves the gate
23 h 16 apart on the timetable, overnight
UA 779 leaves 23 h 16 after AA 9909 arrives on the timetable: more than half a day, so not a connection we count.