BA 541 then UA 949 at Heathrow
Bologna → London → San Francisco
Timetable, London time
14:30BA 541 from Bologna at the gate
13:45UA 949 to San Francisco leaves the gate
23 h 15 apart on the timetable, overnight
UA 949 leaves 23 h 15 after BA 541 arrives on the timetable: more than half a day, so not a connection we count.