Each year, the USCCB Secretariat of Divine Worship publishes the Liturgical Calendar for the Dioceses in the U.S. The liturgical calendar marks the Church year: a sequence of seasons, feasts, and days observed in commemoration of the life, death, and Resurrection of Jesus Christ and of His virtues as exhibited in the lives of the saints. This calendar lists each day’s celebration, rank, liturgical color, and citations for the Lectionary for Mass and Psalter cycle for the Liturgy of the Hours. Thus making sacred the ordinary time of a twelve-month calendar. We inherited this notion from our Jewish ancestors of the Old Testament (O.T.) (Leviticus 23).
The Church calendar observes seven distinct seasons in church life. The Liturgical Year begins on the First Sunday of Advent, then moves to Christmas, Epiphany (concludes with the Feast of Jesus’ Baptism), Ordinary Time, Lent, Triduum or Three Days/ Easter, Pentecost and Ordinary Time again, finishing with the feast of Christ the King. The Church in the course of the year unfolds the whole mystery of Jesus and this process begins with Sunday worship, which is the cornerstone of the whole liturgical calendar. Each Sunday is a holy day of obligation and six Solemnities are also observed as feasts of precept.
Saints and other celebrations are marked 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 (Vigil), Feasts and Memorials are celebrated over the course of one day and Memorials are either Obligatory or Optional. The feast days usually correspond to the date of death, the birth of the saint into eternal life.
In the Early Church, Christians gathered on the first day of the week (Lord’s Day/Sunday) for the breaking of the bread (Acts 20:7). Fridays were designated as days of penance and sacrifice, in honor of our Lord’s sacrifice of Himself for our sins on Good Friday. Wednesdays were marked as a day of penance and prayer. By the 10th century, our Blessed Mother was honored on Saturdays.
The Church’s desire to see Jesus in all things and all things in light of Jesus influences the selected scriptural readings. Typology treats events and images in the Old Testament as prefiguring the life of Jesus and the Church. The fullness of God’s revelation as expressed in Jesus exposes patterns and symbols in His earlier dealings with mankind that we might otherwise miss; i.e. Abraham’s willingness to sacrifice Isaac is a type of Jesus’ divine sacrifice and resurrection. For each day, the Old Testament readings and the responsorial psalm are selected because of their typological relationship to the Gospel reading. We follow a two-year cycle for daily Mass (each of the three Synoptics Gospel is read for a part of the year) and a Three-year cycle for Sundays (A-Matt., B-Mark, C-Luke). We can prepare for Mass by reading the scripture readings ahead of time and praying using lectio divina (a meditative way of reading the bible). We can chose a saint whose feast is celebrated during the week to learn of and from.
Resources: Catholic Answers and New Advent MAC AND MARCIA HICKEY