"Christ yesterday and today… All time belongs to him and all the ages." (Easter Vigil)
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.
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 marvellous 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 2020 began the 2021 liturgical year).
The organization of each liturgical year is governed by the Church and ultimately integrated into a liturgical calendar.
Sunday has a unique liturgical category: "the Lord's day is the original feast day", and it "must be observed in the universal Church as the primordial holy day of obligation". 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. These are: