Christmas Day falls on a Monday this year, so Christmas Eve is the fourth Sunday of Advent. The fourth Sunday of Advent and Christmas Day are separate days of obligation. Mass-goers should not merge the two.

The Sunday Mass obligation (fourth Sunday of Advent) may be fulfilled in the usual way from the evening of Sat., Dec. 23, through the morning of Sun., Dec. 24. The Christmas Mass obligation may be fulfilled from late afternoon Sun., Dec. 24, through Mon., Dec. 25.

On the following weekend, the solemnity of Mary, the Mother of God -- a holy day -- falls on Mon., Jan. 1. In this instance, it is not a holy day of obligation, although Masses will be celebrated and Catholics are encouraged to attend.