17th March is Saint Patrick's Day

Saint Patrick's Day is celebrated worldwide by Irish people and increasingly by non-Irish people (usually in Australia and North America). Celebrations are generally themed around all things Irish and, by association, the colour green. Both Christians and non-Christians celebrate the secular version of the holiday by wearing green or orange, eating Irish food and/or green foods, imbibing Irish drink (such as Guinness or Baileys Irish Cream) and attending parades. Primary and high schools also often dress up in green on st Patricks day.

The St. Patrick's Day parade in Dublin, Ireland is part of a five-day festival; over 500,000 people attended the 2006 parade. The St. Patrick's Day parade was first held in Boston in 1761, organized by the Charitable Irish Society. New York City's celebration began on 18 March 1762 when Irish soldiers in the British army marched through the city, and the New York parade is the largest, typically drawing two million spectators and 150,000 marchers.

The predominantly French-speaking Canadian city of Montreal, in the province of Québec has the longest continually running Saint Patrick's day parade in North America, since 1824. Ireland's cities all hold their own parades and festivals, including Dublin, Cork, Belfast, Derry, Galway, Kilkenny, Limerick, and Waterford. Parades also take place in other Irish towns and villages. The city's flag has the Irish emblem, the shamrock, in one of its corners.

Saint Patrick's Day, colloquially St. Paddy's Day or Paddy's Day, is an annual feast day which celebrates Saint Patrick, one of the patron saints of Ireland, and is generally celebrated on March 17.

The day is the national holiday of Ireland. It is a bank holiday in Northern Ireland and a public holiday in the Republic of Ireland, Montserrat, and the Canadian province of Newfoundland and Labrador. In the rest of Canada, the United Kingdom, Australia, the United States and New Zealand, it is widely celebrated but is not an official holiday. 

It became a feast day in the Roman Catholic Church due to the influence of the Waterford-born Franciscan scholar Luke Wadding in the early part of the 17th century, and is a holy day of obligation for Roman Catholics in Ireland. The date of the feast is occasionally, yet controversially, moved by church authorities when March 17 falls during Holy Week; this happened in 1940 when Saint Patrick's Day was observed on April 3 in order to avoid it coinciding with Palm Sunday, and happened again in 2008, having been observed on 15 March. March 17 will not fall during Holy Week again until 2160

Americans celebrate the holiday by wearing green clothing. Many people, regardless of ethnic background, wear green-coloured clothing and items. Traditionally, those who are caught not wearing green are pinched, though this practice is in fact alien to those who actually come from Ireland.

Some cities paint the traffic stripe of their parade routes green. Chicago dyes its river green (see picture on the right) and has done so since 1961 when sewer workers used green dye to check for sewer discharges and got the idea to turn the river green for St. Patrick's Day. Indianapolis also dyes its main canal green. Savannah dyes its downtown city fountains green. University of Missouri Rolla - St Pat's Board Alumni paint 12 city blocks kelly green with mops before the annual parade.

(extracts from "The Free Dictionary") 

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