How often do Jubilee Years occur?

It depends!

While the Old Testament Jubilee years under the Mosaic Law were every 50 years, Boniface VIII originally declared Jubilee years would take place every 100 years. It didn’t take long for this to be shortened to 50 years–in fact the second Jubilee was held in 1350. The Romans hoped that this meant Pope Clement VI would return to Rome from Avignon, but he did not. The 50 years was later shortened to 25 years, so that more people could participate in a Jubilee Year in their lifetime.

In addition to the “ordinary” Jubilees that occur every 25 years, a Pope can call an “extraordinary” Jubilee whenever he feels there is a strong need for peace and grace. For example, Pius XI called an Extraordinary Jubilee in 1933 to commemorate the 19th centenary of human redemption. Pope John Paul II called an Extraordinary Jubilee in 1983 for the 1950th anniversary of human redemption. Pope Francis called an Extraordinary Jubilee of Mercy from December 8, 2015-November 20 2016.