Pope Francis has declared an Extraordinary Jubilee Year of Mercy to be a "special time for the Church" in which Catholics throughout the world recall and celebrate God's mercy.
The tradition of a Jubilee Year, also called a Holy Year, can be traced back to the Old Testament, when the Law of Moses decreed special years to be times of forgiveness of debts and other acts of reconciliation among people.
Since 1475, a Holy Year has been declared roughly every 25 years. The last Holy Year was in 2000. Sometimes the pope calls for an "extraordinary" Jubilee Year that occurs outside the regular interval - the Year of Mercy is an extraordinary Jubilee.