Holy days are like Sundays in that Catholics must attend Mass, and if possible, refrain from unnecessary servile work.

In the United States Holy Days of Obligation are:

• January 1, the solemnity of Mary, Mother of God
• Thursday of the Sixth Week of Easter, the solemnity of the Ascension.
• August 15, the solemnity of the Assumption of the Blessed Virgin Mary.
• November 1, the solemnity of All Saints.
• December 8, the solemnity of the Immaculate Conception.