UA 3901 then UA 2491 at Houston
Phoenix → Houston → San Diego
Timetable, Houston time
09:39UA 3901 from Phoenix at the gate
09:30UA 2491 to San Diego leaves the gate
23 h 51 apart on the timetable, overnight
UA 2491 leaves 23 h 51 after UA 3901 arrives on the timetable: more than half a day, so not a connection we count.