Chapter VIII-A. Masses and Prayers for Various Needs and Occasions
326. For well-disposed Christians the liturgy of the sacraments and sacramentals causes almost every event in human life to be made holy by divine grace that flows from the paschal mystery.  The Eucharist, in turn, is the sacrament of sacraments. Accordingly, the Missal provides formularies for Masses and prayers that may be used in the various circumstances of Christian life, for the needs of the whole world, and for the needs of the Church, both local and universal.
327. In view of the broad options for choosing the readings and prayers, the Masses for various needs and occasions should be used sparingly, that is, when the occasion requires.
328. In the Masses for various needs and occasions, unless otherwise indicated, the weekday readings and the chants between them may be used, if they are suited to the celebration.
329. The Masses for various needs and occasions are of three types:
a) the ritual Masses, which are related to the celebration of certain sacraments or sacramentals;
b) the Masses for various needs and occasions, which are used either as circumstances arise or at fixed times;
c) the votive Masses of the mysteries of the Lord or in honor of Mary or a particular saint or of all the saints, which are options provided in favor of the faithful's devotion.
330. Ritual Masses are prohibited on the Sundays of Advent, Lent and the Easter season, on solemnities, on days within the octave of Easter, on all Souls, on Ash Wednesday, and during Holy Week. In addition, the norms in the ritual books or in the Masses themselves also apply.
331. From the selection of Masses for various needs and occasions, the competent authority may choose Masses for those special days of prayer that the conferences of bishops may decree during the course of the year.
332. In cases of serious needs or pastoral advantage, at the direction of the local Ordinary or with his permission, an appropriate Mass may be celebrated on any day except solemnities, the Sundays of Advent, Lent, and the Easter season, days within the octave of Easter, on All Souls, Ash Wednesday, and during Holy Week.
333. On obligatory memorials, on the weekdays of Advent until December 16, of the Christmas season after January 2, and of the Easter season after the octave of Easter, Masses for various needs or occasions are per se forbidden. But if some real need or pastoral advantage requires, at the discretion of the rector of the church or the priest celebrant, the Masses corresponding to such need or advantage may be used in celebration with a congregation.
334. On weekdays in Ordinary Time when there is an optional memorial or the office is of that weekday, any Mass or prayer for various needs and occasions is permitted, but ritual Masses are excluded.