A: The Code of Canon Law lists 10 holy days of obligation besides Sunday: Holy Mary the Mother of God (January 1), the Epiphany (January 6), St. Joseph (March 19), the Ascension (Thursday of the Sixth Week of Easter), the Body and Blood of Christ (Thursday after Trinity Sunday), Saint Peter and Saint Paul the Apostles (June 29), the Assumption (August 15), All Sts. (November 1), the Immaculate Conception (December 8), and the Nativity of our Lord Jesus Christ (December 25) (Canon 1246 §1).
Local bishops’ conferences can add to this list (for instance, St. Patrick’s Day on March 17 is a holy day of obligation in Ireland), remove days from the list, or transfer some days to a Sunday (see Canon 1246 §2). In the United States, for example, the bishops have removed the Solemnity of St. Joseph on March 19 and the Solemnity of Sts. Peter and Paul on June 29 from the National Calendar, thus reducing the number of holy days of obligation to eight. The United States bishops have also transferred the Epiphany (traditionally on January 6) to the Sunday between January 2 and 8, and the Body and Blood of Christ, customarily observed on Thursday after Trinity Sunday, to the Sunday following Trinity Sunday. Further, many ecclesiastical provinces (groups of dioceses) have transferred the Ascension of the Lord from Thursday of the Sixth Week of Easter—40 days after the Resurrection—to the Seventh Sunday of Easter.
After these removals or transfers, this leaves as few as five holy days of obligation in the dioceses of the United States: Holy Mary the Mother of God, January 1; the Assumption of Mary, August 15; All Saints Day, November 1; the Immaculate Conception, December 8; and Christmas, December 25. The first three of these holy days—Holy Mary the Mother of God, her Assumption, and All Saints—cease to be obligatory if they fall on a Saturday or a Monday. Only the Immaculate Conception and Christmas retain their obligatory character, regardless of the day of the week.
—Answered by the Editors