BA 633 then VS 155 at Heathrow
Athens → London → Las Vegas
Timetable, London time
18:25BA 633 from Athens at the gate
17:40VS 155 to Las Vegas leaves the gate
23 h 15 apart on the timetable, overnight
VS 155 leaves 23 h 15 after BA 633 arrives on the timetable: more than half a day, so not a connection we count.