AA 2230 then UA 521 at Houston
Miami → Houston → Boston
Timetable, Houston time
23:58AA 2230 from Miami at the gate
18:35UA 521 to Boston leaves the gate
18 h 37 apart on the timetable, overnight
UA 521 leaves 18 h 37 after AA 2230 arrives on the timetable: more than half a day, so not a connection we count.