St Andrew’s feast day is celebrated on 30 November each year. His symbol is the saltire, as that’s the shape of the cross he was crucified on.
There are several legends linking St Andrew with the Scots – his relics are supposed to have been brought to Scotland from Constantinople. There’s also the legend that, before the Battle of Athelstaneford in the late eighth century, King Angus saw a saltire-shaped cloud formation, declared that St Andrew was watching over his armies, and promised to make him his patron saint if they were victorious.
Historically, perhaps the most likely reason is that St Columba and the Celtic Christians based in Iona wished to claim Andrew as their patron because St Peter was the patron of the Roman Christians – Andrew was called by Jesus of Nazareth to be an Apostle before Peter was, so making Andrew the patron of the Scottish church was a means of trumping the Church led by Rome.