Solemnity of the Immaculate Conception of the Blessed Virgin Mary

The United States Bishops’ Committee on the Liturgy has provided the following exception to this Holy Day of Obligation: When December 8 falls on a Sunday, the observance is transferred to Monday, December 9, and there is no obligation to participate in Mass.
Because Our Lady of the Immaculate Conception is the patron saint of the United States of America, when December 8 falls on a Saturday or a Monday, the obligation to participate in Mass remains.