UA 3851 then B6 416 at San Francisco
Rio De Janeiro → San Francisco → New York JFK
Timetable, San Francisco time
17:41UA 3851 from Rio De Janeiro at the gate
14:55B6 416 to New York JFK leaves the gatealso SQ 1548
21 h 14 apart on the timetable, overnight
B6 416 leaves 21 h 14 after UA 3851 arrives on the timetable: more than half a day, so not a connection we count.