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. The number of additional Days of Obligation vary between countries, from 1 in Hong-Kong to 10 in Vatican.
Holy Days of Obligation in the 2016 Year
All the Days of Obligation observed in the United States are listed below.
Is obligatory in 2016?
All Sundays are obligatory for the faithful to participate in the Mass
The number of Days of Obligation vary from year to year, because the percept to attend Mass is lifted (abrogated) if any of the following days:
1 January (Solemnity of Mary, Mother of God),
15 August (Feast of the Assumption),
1 November (Solemnity of All Saints)
falls on a Saturday or on a Monday. The faithful, however, are encouraged to attend Mass on those days.
Ascension is the Day of Obligation only in the ecclesiastical provinces of Boston, Hartford, New York, Newark, Omaha, and Philadelphia; the others have transferred this celebration to the following Sunday.
In Hawaii since 1992 the only observed Days of Holy Obligation (except Sundays) are Feast of the Immaculate Conception and Christmas.
Special Dates of Prayer
Apart from days of obligation in the Catholic Church there are also often designated additional — Special Days of Prayer, in which the faithful pray for some important intentions chosen by the Church. In those days the faithful are usually not obliged to attend Mass, but they are asked to observe these days in their devotions or private prayer. For example in 2012 there are few Days of Prayer designated for the Archdiocese of San Francisco:
January 1, 2012 — Day of Prayer for World Peace (Solemnity of Mary, Mother of God),
February 26, 2012 — Day of Prayer for the General Needs of Humankind (First Sunday of Lent)
September 3, 2012 — Day of Prayer for Human Rights and Labor (Labor Day)
November 22, 2012 — Day of Prayer for the Fruits of the Earth (Thanksgiving Day)