UA 2376 then UA 2621 at Houston
Atlanta → Houston → Austin
Timetable, Houston time
20:26UA 2376 from Atlanta at the gate
20:25UA 2621 to Austin leaves the gate
23 h 59 apart on the timetable, overnight
UA 2621 leaves 23 h 59 after UA 2376 arrives on the timetable: more than half a day, so not a connection we count.