IB 421 then IB 5376 at Barcelona
Madrid → Barcelona → Firenze
Timetable, Barcelona time
19:15IB 421 from Madrid at the gatealso LL 3021, VY 5122, AV 6170, QR 6971
18:45IB 5376 to Firenze leaves the gatealso LL 5376, VY 6076
23 h 30 apart on the timetable, overnight
IB 5376 leaves 23 h 30 after IB 421 arrives on the timetable: more than half a day, so not a connection we count.