4 We have thought it opportune to use an Encyclical Letter to recall these acts of Our Predecessors that are so closely bound up with such happy memories, Venerable Brethren, now that We are approaching the 100th anniversary of the day—August 4, 1859—on which this holy man, completely broken from forty years of the most tireless and exhausting labors, and already famous in every corner of the world for his holiness, passed on most piously to his heavenly reward.
Source: Sacerdotii Nostri Primordia (Vatican.va)