The Feast of the Divine Mercy was instituted by Pope John Paul II, the Sunday after Easter.  During the Homily, the Pope declared the second Sunday of Easter (the Sunday that follows the Resurrection) as the "Sunday of the Divine Mercy". In his homily, the Pope pronounced the following words:

By instituting this Feast, the Pope concluded the task that Our Lord Jesus had assigned to Saint Faustina in Poland 69 years ago: In February of 1931 Jesus told her: "I desire that there be a Festival of My Mercy."

Just as Jesus had desired it, this Feast is extolled with the plenary indulgence (complete forgiveness of sins and punishment): “The soul that will go to Confession and receive Holy Communion shall obtain complete forgiveness of sins and punishment. Do not let any soul be afraid to draw near to Me.” (Diary 699) "The miracle of the Divine Mercy restores that soul to all its fullness." (Diary 1448)

The Feast of the Divine Mercy is at the central place of the devotion to the Divine Mercy, as requested by Our Lord to Saint Faustina. The will of the Lord, with respect to the institution of this Feast, was declared in His first revelations to Saint Faustina. There were a total of fourteen revelations regarding this Feast.

This Feast also marked the death of Pope John Paul II. Our Lord wanted to give great importance to our Pope in this Feast, emphasizing with it his departure to the eternal life. Pope John Paul II had been a faithful supporter and promoter of the Divine Mercy, both with his teaching and with his life. The Pope affirmed that "the Mercy is the only hope for the world", as Jesus had declared.

The Holy Father’s posthumous message, was read in his honor during the first Divine Mercy Sunday Mass in St Peter’s Square in Vatican City.

The main purpose of The Feast of the Divine Mercy is to instill the following message into the heart of each person: God is our Merciful Father and loves us all dearly. He told us: "the greater the sinner, the greater need he has of My mercy."(Diary 723) In this message, our Lord asks us to have full confidence in the Mercy of God, and tells us that we always need to be merciful with our neighbors in our words, actions and prayers... “because even the strongest faith is of no avail without works."(Diary 742)

Therefore, in order to celebrate this Feast appropriately, we need to pray the Divine Mercy Chaplet and  the Novena to the Divine Mercy (start the Novena on Good Friday); go to confession (always preceded by a good examination of conscience), and receive the Holy Communion the day of the Feast of the Divine Mercy.

Karol Wojtyla, "Pope John Paul ll", had spent his whole earthly life as the Servant of God, proclaiming the Divine Mercy. His life had been concluded in the Vigil of the Feast of this Mystery, which he had instituted. Pope John Paul ll was beatified by his successor, Pope Benedict XVI, on May 1, 2011, on the Feast of the Divine Mercy. Pope Francis also chose "Feast of Divine Mercy" as a very significant date, April 27, 2014 for the canonization of Blessed John Paul II.