Whenever marriage is celebrated within Mass, the Ritual Mass for the celebration of marriage is used, along with white vestments. If, however, the celebration coincides with a day listed in nn. 1-4 of the Table of Liturgical Days, the Mass of the day is used with its own proper readings, plus the nuptial blessing and if appropriate the final blessing of the Ritual Mass og Marriage.
If however, in the Christmas season, or in Ordinary Time, the sacrament of marriage is celebrated within a Mass at which the parish community participates, the Sunday Mass is used. Since, however the Liturgy of the Word is of great moment in the celebration of marriage for the catechesis regarding the sacrament and the duties conferred upon the spouses, in case whre the Ritual Mass for the celebration of marriage is not used, one of the reading may be taken from among those provided for the celebration of marriage (OM, 34).
If marriage is celebrated on a day of penitential character, especially within Lent, the parish priest should advice that account be taken of that character. The celebration of marriage on Good Friday and on the day following Holy Saturday, is absolutely forbidden (OM, 32).