Christmas this year is on a Monday. Does a Christmas Vigil Mass Sunday evening satisfy the obligation for both Sunday Mass and Christmas Mass?
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 (source).
In the United States, going to Sunday daytime Mass on Christmas Eve will not fulfill the holy day obligation for Christmas. Catholics in the U.S. therefore must attend a Mass celebrated for Christmas Day.
Parishes may offer evening Christmas Masses on Christmas Eve. Here, then are the possibilities: A Catholic could go to a Sunday daytime Mass for Sunday and a Christmas vigil Mass on Christmas Eve for Christmas. Or, he could go to one Mass on Sunday for Christmas Eve and one on Monday for Christmas Day. Or, he could go to a Saturday vigil Mass on December 23 for Sunday and either an evening Christmas Mass on Christmas Eve or a daytime Christmas Mass on Christmas Day.
The holy day obligation for the Solemnity of Mary, Mother of God, on January 1 is not binding this year because it will fall on Monday.