Pius X

The Week (in fact, Octave) of Prayers for the Unity of the Christians, with all indulgencies connected with it, was celebrated between Ascension and Pentecost under Leo XIII. St. Pius X set a new date – 18-25 January. It means that the Octave begins on the day of ancient feast of the Saint Peter’s Cathedral in Rome (which was abolished in the new calendar and joined with the feast of Saint Peter’s Cathedral in Antioch) and ends on the day of liturgical commemoration of the Conversion of St. Paul, a tenacious enemy of Christians. This choice highlighted the two elements indispensable to achieve the unity with the Church: to renounce one’s errors and to acknowledge the primate of the Bishop of Rome.