Divine Mercy Sunday: St. Faustina’s Diary records 14 occasions when Jesus requested that a Feast of Mercy (Divine Mercy Sunday) be observed, for example:

My daughter, tell the whole world about My inconceivable mercy. I desire that the Feast of Mercy be a refuge and shelter for all souls, and especially for poor sinners. On that day the very depths of My tender mercy are open. I pour out a whole ocean of graces upon those souls who approach the Fount of My mercy. The soul that will go to Confession and receive Holy Communion shall obtain complete forgiveness of sins and punishment. … Let no soul fear to draw near to Me. … It is My desire that it be solemnly celebrated on the first Sunday after Easter. Mankind will not have peace until it turns to the Fount of My Mercy.

—St. Faustina, Diary, no. 699

On May 5, 2000, five days after the canonization of St. Faustina, the Vatican decreed that the Second Sunday of Easter would henceforth be known as Divine Mercy Sunday.