Your Question: What are the Holy Days of Obligation for Roman Catholics?

In addition to Sundays (or anticipation Masses on Saturday evening), the HolyDays of Obligation for Roman Catholics in the United States are as follows:

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;
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 (that means the obligation to attend Mass is lifted)

Also, in the some dioceses and archdioceses, Milwaukee included, the solemnity of the Ascension is tranferred to a Sunday. Thus, the obligation to attend Mass on Thursday is suspended.