St. Patrick's day

Saint Patrick's Day was made an official Christian feast day in the early seventeenth century and is observed by the Catholic Church, the Anglican Communion (especially the Church of Ireland), the Eastern Orthodox Church and Lutheran Church. The day commemorates Saint Patrick and the arrival of Christianity in Ireland, as well as celebrating the heritage and culture of the Irish in general Christians also attend church services, and the Lenten restrictions on eating and drinking alcohol are lifted for the day, which has encouraged and propagated the holiday's tradition of alcohol consumption.

(http://en.wikipedia.org/wiki/Saint_Patrick's_Day)