Divine Mercy Sunday
How is this different than just going to Confession on any other day? When we commit sin, we apologize to Jesus in the confessional. Jesus accepts our apology and our relationship with Him is repaired so that we may return to Communion with Him. But, after our death, we will still have to pay the price in purgatory for the damage our sins have caused.
On Divine Mercy Sunday, when we receive Confession and Communion, our time in purgatory is completely dismissed. Pope St. John Paul II presented this Decree of the Holy See granting the following Plenary Indulgence, as well, based on the message of Jesus to St. Faustina:
"A plenary indulgence, granted under the usual conditions (sacramental confession, Eucharistic communion and prayer for the intentions of Supreme Pontiff) to the faithful who, on the Second Sunday of Easter or Divine Mercy Sunday, in any church or chapel, in a spirit that is completely detached from the affection for a sin, even a venial sin, take part in the prayers and devotions held in honour of Divine Mercy, or who, in the presence of the Blessed Sacrament exposed or reserved in the tabernacle, recite the Our Father and the Creed, adding a devout prayer to the merciful Lord Jesus (e.g. Merciful Jesus, I trust in You!)..."