"Christ yesterday and today… All time belongs to him and all the ages." (Easter Vigil)
The first words of the Universal Norms on the Liturgical Year and the Calendar, drawn from the Second Vatican Council's Constitution on the Sacred Liturgy, summarize the profound meaning of the liturgical celebrations of the Church and their organization:
Holy Church celebrates the saving work of Christ on prescribed days in the course of the year with sacred remembrance. Each week, on the day called the Lord's Day, she commemorates the Resurrection of the Lord, which she also celebrates once a year in the great Paschal Solemnity, together with his blessed Passion. In fact, throughout the course of the year the Church unfolds the entire mystery of Christ and observes the birthdays of the Saints. (no. 1)
The liturgical year consists of a seasonal cycle and a sanctoral cycle, called the Proper of Time and the Proper of Saints, respectively. Both are organized and published in a liturgical calendar, which is also enriched by observances proper to local Churches, whether national, diocesan, parish-level, or religious community. The Paschal Mystery of Jesus Christ—his suffering, death, and resurrection—is continuously proclaimed and renewed through celebrating the events of his life and in the feasts of the Blessed Virgin Mary and the saints.
The liturgical year is made up of six seasons:
The mystery of Christ, unfolded through the cycle of the year, calls us to live his mystery in our own lives. This call is best illustrated in the lives of Mary and the saints, celebrated by the Church throughout the year. There is no tension between the mystery of Christ and the celebration of the saints, but rather a marvelous harmony. The Blessed Virgin Mary is joined by an inseparable bond to the saving work of her Son, and the feasts of all the saints proclaim the wonderful works of Christ in his servants and offer the faithful fitting examples for their imitation.
Each liturgical year begins on the First Sunday of Advent during the preceding calendar year (i.e., the First Sunday of Advent in 2019 began the 2020 liturgical year).
The organization of each liturgical year is governed by the Church and ultimately integrated into a liturgical calendar.
The Second Vatican Council brought renewed emphasis to Sunday as a unique liturgical category: "the Lord's day is the original feast day" (Sacrosanctum Concilium, no. 106), and it "must be observed in the universal Church as the primordial holy day of obligation" (Code of Canon Law, canon 1246 §1). Thus, only a limited number of feasts of the Lord or the saints may take the place of the scheduled Sunday celebration.
Saints and other celebrations are distinguished in accordance with the importance assigned to each one: each is a Solemnity, Feast, or Memorial. Sundays and Solemnities begin their celebration on the evening before, Feasts and Memorials are celebrated over the course of one day, and Memorials are either Obligatory or Optional.
Finally, holy days of obligation (also known as feasts of precept) are days when the faithful are obliged to participate at Mass and abstain from unnecessary work or other activities which hinder the suitable relaxation of mind and body. Each Sunday is a holy day of obligation, and six Solemnities are also observed as feasts of precept in the United States.
The General Roman Calendar includes "both the entire cycle of celebrations of the mystery of salvation in the Proper of Time, and that of those Saints who have universal significance and therefore are obligatorily celebrated by everyone, and of other Saints who demonstrate the universality and continuity of sainthood within the People of God" (Universal Norms on the Liturgical Year and the Calendar, no. 49).
After the reforms of the Second Vatican Council, the General Roman Calendar was first promulgated in 1969 by Pope Saint Paul VI, and has subsequently been amended over the years by the Holy See with new celebrations. The last major revision was in 2002, but since the publication of the Roman Missal, Third Edition, the following celebrations have been added to the General Roman Calendar or otherwise changed:
The calendar for the universal Church is complemented in this country by the Proper Calendar for the Dioceses of the United States of America, most recently approved in 2010. Two Optional Memorials have been added to the U.S. Proper Calendar since the 2011 implementation of the Roman Missal, Third Edition:
Each year, the USCCB Secretariat of Divine Worship publishes the Liturgical Calendar for the Dioceses of the United States of America. This calendar lists each day's celebration, rank, liturgical color, citations for the Lectionary for Mass, and Psalter cycle for the Liturgy of the Hours. It is primarily used by authors of ordines and other liturgical aids published to foster the celebration of the liturgy in our country, but may also be used by anyone who purchases or downloads a copy.