DETROIT — The Solemnity of the Immaculate Conception, which this year falls on Saturday, Dec. 8, is a holy day of obligation in the United States.

However, because Sunday, Dec. 9, is also the second Sunday of Advent, there will be two Mass obligations that weekend.

Masses celebrated either Friday evening (Dec. 7) or Saturday morning (Dec. 8 ) will fulfill a Catholic’s obligation for the Immaculate Conception holy day. A separate obligation for the second Sunday of Advent will be fulfilled by Masses either Saturday evening (Dec. 8 ) or Sunday (Dec. 9).

As the U.S. bishops’ Committee on Divine Worship explains, “In the Table of Liturgical Days, a solemnity of the Virgin Mary ranks lower than a Sunday of Advent; therefore, the Immaculate Conception will end on the afternoon of Saturday, Dec. 8.

“On Saturday evening, Evening Prayer I of the Second Sunday of Advent is celebrated instead of Evening Prayer II of the Immaculate Conception, and Masses are that of the Second Sunday of Advent.”

Because the Immaculate Conception is the patronal feast day of the United States, it is always a holy day of obligation unless Dec. 8 falls on a Sunday — which will happen next year. In that case, the solemnity will be transferred to Monday, Dec. 9, but not the obligation, which will be fulfilled by attending Sunday Mass.

The Immaculate Conception refers to the Blessed Virgin Mary’s being miraculously preserved by God from the stain of original sin from the moment of her conception, in preparation for her eventual role as the vessel that would carry Jesus into the world. Some theologians see a parallel between Mary’s preservation from sin and the pure gold that was required in the Ark of the Covenant, which carried God’s presence under the Old Covenant.

The Immaculate Conception is not to be confused with the virgin birth, the belief that Jesus was born of a perpetual virgin. Mary herself, the Church holds, was conceived naturally by her parents, Joachim and Anne.

The patronal feast day is when Americans celebrate the Mother of God as the patron saint of our country.