For many countries and places, Saint Patrick's day is a good excuse for a party. However, in Ireland, traditions in the past meant the celebrations were usually somber. No alcohol was allowed to be soled on the day in Ireland until that law was repealed in the 1960s. The day involved mass in the morning and then a military parade followed, reflecting the influence of the conflicts between the Unionist and nationalist elements from the early 20th century.
It was in the 1960s that people began to adopt the US version of celebrations, with the day often being associated with heavy drinking and parades. Rather than a somber day, it became more celebratory in Ireland as well.