B6 393 then UA 534 at Denver
Boston → Denver → Great Falls
Timetable, Denver time
11:47B6 393 from Boston at the gate
11:45UA 534 to Great Falls leaves the gate
23 h 58 apart on the timetable, overnight
UA 534 leaves 23 h 58 after B6 393 arrives on the timetable: more than half a day, so not a connection we count.