(CNN)Here's a look at what you need to know about St. Patrick's Day, celebrated March 17th of every year.
St. Patrick's Day is the feast day of St. Patrick, the patron saint of Ireland.
St. Patrick is called a Christian missionary and the Apostle of Ireland.
Patron saints are chosen to protect the interests of a country, place, group, trade or profession, or activity, and to intercede for them in heaven.
St. Patrick is responsible for converting the people of Ireland to Christianity.
385 A.D - Born in Britain, but is not Irish.
At sixteen, he was brought to Ireland as a slave.
He escaped six years later and became a priest.
Following a vision, he returned to Ireland to Christianize the Irish people.
He is credited with having driven the snakes out of Ireland. However, most biologists maintain there never were snakes in Ireland.
March 17, 461 A.D - St. Patrick dies.
In Ireland, St. Patrick's Day is a national holiday with banks, stores, and businesses closing for the day.
It has primarily been celebrated as a religious holiday.
1737 - The first St. Patrick's Day celebration in the United States is held in Boston.
According to the U.S. Census, 33.3 million U.S. residents claimed Irish ancestry in 2013. This number is more than seven times the population of Ireland (4.6 million).
In the United States, St. Patrick's Day is primarily a secular holiday.
New York City Celebration:
March 17, 1762 - The first official parade in New York City is held.
March 17, 2011 - The 250th New York City St. Patrick's Day Parade is held.
The parade is held on March 17, unless March 17 falls on a Sunday. When this happens, the parade is held on Saturday the 16th.
The parade marches up 5th Avenue, from 44th to 79th streets. It is the world's largest St. Patrick's Day parade with more than 150,000 people marching each year.
September 4, 2014 - The organizers of the New York City St. Patrick's Day Parade announce the first ever LGBT group to march in 2015 under their banner. It represents an end to a ban on openly gay groups in the parade.
March 12, 1955 - The first St. Patrick's Day parade is held.
If the 17th falls on a weekday, the parade is held the Saturday before.
Legend has it St. Patrick used the shamrock to explain the concept of the Holy Trinity, by showing an unbeliever the three-leafed plant with one stalk.
Shamrocks are the national flower/emblem of Ireland.