The Extraordinary Jubilee of Mercy (Iubilaeum Extraordinarium Misericordiae) is a period of prayer held from the Feast of the Immaculate Conception on Dec. 8, 2015 to the Feast of Christ the King on Nov. 20, 2016 (the "Year of Mercy"). The Jubilee was announced March 25 and declared in Pope Francis' papal bull of indiction, Misercordiae Vultus, in April 2015.
The practice of a jubilee year has ancient roots in the Jewish tradition and evidence for it can be found in the Old Testament (for example, see Leviticus 25). The jubilee year was called every fifty years and was a time for forgiveness. It stood as a reminder of God's providence and mercy. The dedication of a year for this emphasis provided the community with a time to come back into right relationship with one another and with God. As the practice of the jubilee year was adopted into the Catholic Church, these themes of mercy, forgiveness, and solidarity continued. (USCCB)
In his homily for for First Vespers for Divine Mercy Sunday, Pope Franics said, "Here, then, is the reason for the Jubilee: because this is the time for mercy. It is the favourable time to heal wounds, a time not to be weary of meeting all those who are waiting to see and to touch with their hands the signs of the closeness of God, a time to offer everyone, everyone, the way of forgiveness and reconciliation. May the Mother of God open our eyes, so that we may comprehend the task to which we have been called; and may she obtain for us the grace to experience this Jubilee of Mercy as faithful and fruitful witnesses of Christ."