We Can all Thank the Pirates for St. Patrick's Day
St. Patrick's Day, celebrated every year on March 17, is a holiday honoring Saint Patrick, the missionary credited with converting the Irish to Christianity in the A.D. 400s. Saint Patrick's real name was Maewyn Succat. For his first 16 years, Maewyn lived a normal life as the son of a wealthy landowner and magistrate in Britain.

At 16, Maewyn was captured and sold into slavery by a group of pirates who raided his village. After six years of herding sheep, Maewyn escaped, went to France and became a priest, adopting the name Patrick.

During his training, Patrick discovered that his calling was to convert Irish pagans to Christianity. He returned to Ireland, established monasteries across the country, set up schools and churches, and converted many with his winning personality. Patrick carried on a very successful mission for thirty years. When he died on March 17, that day was commemorated as St. Patrick's Day.
--From Care2.com