Holy Days of Obligation

In the Catholic Church, Holy Days of Obligation are the days on which the faithful are obliged to participate in the Mass. They have also abstain from unnecessary works, "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." (canon 1247 of the Code of Canon Law).

The list of Days of Obligation includes all Sundays in all countries. Some feasts, e.g. Easter, are always celebrated on Sundays, so they are always obligatory.