In the Catholic Church, Holy Days of Obligation (also called holydays, holidays, or days of obligation) are days on which "the faithful are to refrain from engaging in work or activities that hinder the worship owed to God, the joy proper to the Lord's Day, the performance of the works of mercy, and the appropriate relaxation of mind and body.

Family needs or important social service can legitimately excuse from the obligation of Sunday rest.

The faithful should see to it that legitimate excuses do not lead to habits prejudicial to religion, family life, and health" [CCC 2185].

January 1: The Feast of Mary, the Holy Mother of God
Vigil Mass on Monday, Dec. 31 at 5:00pm or Mass on Tuesday, Jan. 1 at 10:00am will fulfill the Mass obligation.
 
May 30 : Ascension of the Lord (40 days after Easter Sunday)
Celebrated on Sunday, June 2 this year in the Sacramento Diocese. The 5:00pm Vigil Mass on Saturday, June 1 or any Sunday Mass on June 2 will fulfill the Mass obligation.

August 15: Assumption of the Blessed Virgin Mary
Masses to be announced . . . 

November 1: All Saints' Day
Masses to be announced . . .

December 9: The Feast of the Immaculate Conception
Masses to be announced . . .

December 25: Christmas, the Nativity of Our Lord
Masses to be announced . . .