Holy Days of Obligation
In the Catholic Church the Holy Days of Obligation (or less known as the Feasts of Precept) the faithful are obliged to participate in the Mass. Moreover they are to abstain from those works and affairs which hinder the worship to be rendered to God, the joy proper to the Lord’s day, or the suitable relaxation of mind and body (from Canon Law). In addition to Sunday, the days to be observed as holy days of obligation are as follows:
Whenever January 1, the solemnity of Mary, Mother of God, or August 15, the solemnity of the Assumption, or November 1, the solemnity of All Saints, falls on a Saturday or on a Monday, the precept to attend Mass is abrogated (the guidelines to attend Mass are withdrawn).