Saint Patrick’s Day is celebrated annually on March 17, the anniversary of his death in the fifth century.
The Irish have observed this day as a religious holiday for over 1,000 years.
On Saint Patrick’s Day, which falls during the Christian season of Lent, Irish families would traditionally attend church in the morning and celebrate in the afternoon. Lenten prohibitions against the consumption of meat were waived and people would dance, drink and feast–on the traditional meal of Irish bacon and cabbage.
It is a public holiday in the Republic of Ireland, Northern Ireland and it is also widely celebrated in the United Kingdom, Canada, United States, Brazil, Argentina, Australia and New Zealand, especially amongst Irish diaspora.

Who was St Patrick ?

He lived during the 5th century, he is the patron saint of Ireland and its national apostle. He was born in Roman Britain, and was kidnapped and brought to Ireland as a slave at the age of 16. He later escaped, but returned to Ireland and was credited with bringing Christianity to its people.
In the centuries following Patrick’s death (believed to have been on March 17, 461), the mythology surrounding his life became ever more ingrained in the Irish culture : the most well-known legend of Saint Patrick is that he explained the Holy Trinity (Father, Son and Holy Spirit) using the three leaves of a native Irish clover, the shamrock.