The Feast of Mercy is celebrated on the first Sunday after Easter, that is on the Second Sunday of Easter, which is called the Divine Mercy Sunday today. Cardinal Franciszek Macharski was the first one to make it part of the liturgical calendar of the Archdiocese of Cracow (1985) and, later, some Polish bishops instituted the feast in their dioceses. In 1995, at the request of the Polish Episcopal Conference, Holy Father John Paul II instituted the feast in all dioceses in Poland. On the day of Sister Faustina’s canonization, 30th April 2000, the Pope instituted the feast for the whole Church.
The institution of the feast was inspired by a desire of Jesus which was conveyed by Sister Faustina. The Lord Jesus told her: “I want the first Sunday after Easter to be the Feast of Mercy” (Diary 299). “I want the Feast of Mercy to be a refuge and sanctuary for all souls, and especially for poor sinners. On that day the depths of My mercy are open; I pour out a whole sea of graces on souls that approach the fount of My mercy. Any soul that makes its Confession and receives Holy Communion will have its sins and its punishment completely remitted. On that day are open all the Divine floodgates through which graces flow” (Diary 699). In many revelations the Lord Jesus did not only define the place of the feast in the liturgical calendar of the Church but also the reason for its institution, the way it should be prepared, celebrated, and He also spoke about the great promises. The greatest of them is the grace of „complete forgiveness of sins and punishment”. It is connected with Holy Communion received on that day, following a good Confession (without any attachment to the smallest sin), in the spirit of the devotion to the Divine Mercy, that is, trusting God and loving neighbour actively. As the Rev. Professor Ignacy Różycki says, it is a grace greater than plenary indulgence. „Plenary indulgence is only a remission of temporal punishment for the sins committed, however, it is never a remission of the sins themselves. Basically, the most special grace is greater than the graces of the 6 sacraments, apart from the sacrament of baptism, since only the sacramental grace of the holy baptism is the forgiveness of all sins and punishment. However, as far as these promises are concerned, Christ associated the remission of sins and punishment with Holy Communion received during the Feast of Mercy, therefore, as regards this, He raised it to the rank of the 'second baptism’.” In preparation for this feast we are to recite the novena which consists in saying the Chaplet to the Divine Mercy for 9 days. The novena begins on Good Friday. The Lord Jesus said to Sister Faustina: “Tell them that the Feast of Mercy has come from My depths for the consolation of the whole world” (Diary 1517).