This upcoming Good Friday we begin the Divine Mercy Novena. The novena can be found here. I can't stress enough how vital it is for everyone to join in praying this special novena in preparation for Divine Mercy Sunday (the Sunday following Easter Sunday).
According to St. Faustina, Our Lord promises to those who go to confession and communion on this day, the remission of the guilt and the punishment of sins.
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. On that day all the divine floodgates through which grace flow are opened. Let no soul fear to draw near to Me, even though its sins be as scarlet. My mercy is so great that no mind, be it of man or of angel, will be able to fathom it throughout all eternity. (Diary of Sr. Faustina, 699)Many take this to mean that they must go to Confession ON Mercy Sunday. This is not true. To receive the benefits of the Promise one must be in the state of grace. The Lord does not promise the absolution of grave sin on Mercy Sunday, but points us to the Sacrament of Penance. To receive the grace we should be disposed. This is done by a confession near the time of Mercy Sunday. According to the Cardinal of Krakow, the confession which a Catholic makes during Lent in preparation for Easter is sufficient. Priests do not have to provide confession on Mercy Sunday so that Catholics can satisfy this condition. Since it is a Sunday the condition of Communion can be easily satisfied (including at the Saturday Vigil Mass). Our Communion, as our Confession, should be especially devout.
Read more about Divine Mercy Sunday here.