Joe's Fotothing

Saint Patrick is the patron Saint of Ireland.
(This is why Irishmen are often referred to as Paddy's)

Who Was St. Patrick?
St. Patrick, the patron saint of Ireland, is one of Christianity's most widely known figures. But for all his celebrity, his life remains somewhat of a mystery. Many of the stories traditionally associated with St. Patrick, including the famous account of his banishing all the snakes from Ireland, are false, the products of hundreds of years of exaggerated storytelling.
Taken Prisoner By Irish Raiders
It is known that St. Patrick was born in Britain to wealthy parents near the end of the fourth century. He is believed to have died on March 17, around 460 A.D. Although his father was a Christian deacon, it has been suggested that he probably took on the role because of tax incentives and there is no evidence that Patrick came from a particularly religious family. At the age of sixteen, Patrick was taken prisoner by a group of Irish raiders who were attacking his family's estate. They transported him to Ireland where he spent six years in captivity. (There is some dispute over where this captivity took place. Although many believe he was taken to live in Mount Slemish in County Antrim, it is more likely that he was held in County Mayo near Killala.) During this time, he worked as a shepherd, outdoors and away from people. Lonely and afraid, he turned to his religion for solace, becoming a devout Christian. (It is also believed that Patrick first began to dream of converting the Irish people to Christianity during his captivity.)
After more than six years as a prisoner, Patrick escaped. According to his writing, a voice—which he believed to be God's—spoke to him in a dream, telling him it was time to leave Ireland.

To do so, Patrick walked nearly 200 miles from County Mayo, where it is believed he was held, to the Irish coast. After escaping to Britain, Patrick reported that he experienced a second revelation—an angel in a dream tells him to return to Ireland as a missionary. Soon after, Patrick began religious training, a course of study that lasted more than fifteen years. After his ordination as a priest, he was sent to Ireland with a dual mission—to minister to Christians already living in Ireland and to begin to convert the Irish. (Interestingly, this mission contradicts the widely held notion that Patrick introduced Christianity to Ireland.)
The first St. Patrick's Day parade took place not in Ireland, but in the United States. Irish soldiers serving in the English military marched through New York City on March 17, 1762. Along with their music, the parade helped the soldiers to reconnect with their Irish roots, as well as fellow Irishmen serving in the English army.

Saint Patrick's day is celebrated all over the world (almost) on March 17th.