LA 6139 then CZ 1639 at San Francisco
Boston → San Francisco → Miami
Timetable, San Francisco time
23:58LA 6139 from Boston at the gate
23:47CZ 1639 to Miami leaves the gatealso AA 1844, PR 3934, QF 4121, G3 6252, IB 8568
23 h 49 apart on the timetable, overnight
CZ 1639 leaves 23 h 49 after LA 6139 arrives on the timetable: more than half a day, so not a connection we count.