Saint Patrick's DaySaint Patrick's Day (Irish: Lá Fhéile Pádraig) is a religious holiday celebrated internationally on 17 March. It is named after Saint Patrick (c. AD 387–461), the most commonly recognised of the patron saints of Ireland. It originated as a Catholic holiday and became an official feast day in the early 17th century. It has gradually become more of a secular celebration of Irish culture.
It is a public holiday in the Republic of Ireland, Northern Ireland, Newfoundland and Labrador and in Montserrat. It is also widely celebrated by the Irish diaspora, especially in places such as Great Britain, Canada, the United States, Argentina, Australia, New Zealand, and Montserrat, among others.
Source: http://en.wikipedia.org/wiki/Saint_Patrick's_Day