How does your name determine your saints day?

If your given name is also the name of a saint in the calendar of the Catholic Church, you can find the day when that saint is venerated, often the day of his death (if known). For example, the feast day of St. Patrick is March 17. That's easy because it is also widely celebrated as St. Patrick's Day. So if your first name is Patrick, that is your saint's day or feast day. Valentine's Day is February 14, and it used to be the feast of St. Valentine, but that is not in the church calendar anymore. St. Joseph is March 19. St. John is December 27 (for the apostle and evangelist).