Christ’s saving work is celebrated in sacred memory by the Church on fixed days throughout the year. Each week on the day called the Lord’s Day the Church commemorates the Lord’s resurrection. Once a year at Easter, the Church honors the resurrection and passion with the utmost solemnity. In fact through the yearly cycle the Church unfolds the entire mystery of Christ and keeps the anniversaries of the saints.
During the different seasons of the liturgical year, the church, in accord with traditional discipline, carries out the formation of the faithful by means of devotional practices, both interior and exterior, instruction, and works of penance and mercy.
General Norms for the Liturgical Year and Calendar, 1
Our secular lives are ruled by the waxing and waning of the seasons, for some according to the academic year, for others the lunar year, and for many, the fiscal year. But for us as Christians, our lives of prayer and worship are shaped according to the Church year, better known as the liturgical year, the high point of which is Easter. The paschal mystery of Jesus Christ is the center and pivot of all our liturgical celebrations. The Church celebrates this whole mystery by means of the yearly cycle, from his incarnation until the day of Pentecost and the expectation of his return.
The liturgical calendar arranges the celebrations of the liturgical year, beginning with the first Sunday of Advent and concluding on the Saturday after the Solemnity of Christ the King. It is structured according to universal and particular church usages e.g., a diocese or religious order. Here are the Vatican universal norms, published in 1969, which greatly simplified what had been in use before Vatican II. These and the Liturgical Calendar for the Dioceses of the Unites States are the basis for the Ordos published by the various dioceses and religious congregations. This is also found at the beginning of the Roman Missal.
Each year the USCCB Secretariat for Liturgy publishes the official Liturgical Calendar for the Dioceses of the United States of America. The calendar is used by publishers of parish calendars, desk calendars, and ordos in the preparation of their products and lists each day’s celebration, rank, liturgical color, Lectionary citations and Psalter cycle for the Liturgy of the Hour.