"The dates of Patrick's life cannot be fixed with certainty but there is broad agreement that he was active as a missionary in Ireland during the second half of the 5th century. Early medieval tradition credits him with being the first bishop of Armagh and Primate of Ireland, and they regard him as the founder of Christianity in Ireland, converting a society practising a form of Celtic polytheism. He has been generally so regarded ever since, despite evidence of some earlier Christian presence in Ireland.
According to the Confessio of Patrick, when he was about 16, he was captured by Irish pirates from his home in Britain, and taken as a slave to Ireland, looking after animals, where he lived for six years before escaping and returning to his family. After becoming a cleric, he returned to northern and western Ireland. In later life, he served as a bishop, but little is known about the places where he worked. By the seventh century, he had already come to be revered as the patron saint of Ireland.
Saint Patrick's Day is observed on 17 March, the supposed date of his death. It is celebrated inside and outside Ireland as a religious and cultural holiday. In the dioceses of Ireland, it is both a solemnity and a holy day of obligation; it is also a celebration of Ireland itself."