Divine Mercy
When St. Pope John Paul canonized Sr. Faustina (making her St. Faustina), he also, on the same day, surprised the entire world by establishing Divine Mercy Sunday (the feast day associated with the message) as a feast day for the entire Church. The feast day falls on the Second Sunday of the Easter season. On that day, John Paul II declared, "This is the happiest day of my life." For more information: https://www.thedivinemercy.org/