That day marks the anniversary of the death of a Christian missionary known as Patrick. At the age of 16, he was captured and taken to Ireland as a slave. During this period, he became very religious and after six years he fled back to his family, as a missionary. He said to have an important rule to convert the inhabitants of Ireland to Christianity. He died on March 17, probably in the year 461 or 493.
The most widely-seen St Patrick’s Day symbols are the colors green, and sometimes orange, and the shamrock (symbol of Ireland and a registered trademark of the Republic of Ireland, usually confused with the four-leaves clover and his luck).
St Patrick’s Day is not a public holiday in other parts of Canada. Schools, organizations, businesses, stores and post offices are open as usual. Some organizations may arrange St Patrick’s Day parties, but these do not usually disrupt normal affairs. Public transport services run on their regular timetables. In cities, where parades or large public events are held, there may be some congestion or road closures.
One of the biggest St. Patrick’s Day parties in Canada happens right in the heart of Vancouver! CelticFest is a celebration amongst all nations of Celtic descent, and this year the St. Patty’s Day celebration is a virtual event!
Nowadays people who have an Irish background may held some Irish themed parties with typical Irish music, food (lamb and root vegetables, or mashed potatoes with kale or cabbage) and- most of all- drinks: dark beer, whiskey.
source: https://www.timeanddate.com/holidays/canada/st-patrick-day
http://www.lejournalinternational.info/it/canada-a-saint-patrick-canada-se-met-vert/