In addition to Sunday, the days to be observed as holy days of obligation in the Latin Rite dioceses of the United States of America, in conformity with canon 1246, are as follows:

January 1, the solemnity of Mary, Mother of God (see exceptions below)
Thursday of the Sixth Week of Easter, the solemnity of the Ascension 
August 15, the solemnity of the Assumption of the Blessed Virgin Mary (see exceptions below)
November 1, the solemnity of All Saints (see exceptions below)
December 8, the solemnity of the Immaculate Conception of Mary
December 25, the solemnity of the Nativity of Our Lord Jesus Christ

Whenever January 1, the solemnity of Mary, Mother of God, or August 15, the solemnity of the Assumption, or November 1, the solemnity of All Saints, falls on a Saturday or on a Monday, the precept to attend Mass is abrogated.