The basic ecclesiastical year was set by the time of Saint Gregory the Great. Over time additional feast days would be added to Holy Masses that were part of both the Proper of the Season as well as Masses that were part of the Sanctoral Calendar.
The year begins on the first Sunday of Advent, that is, on the Sunday next, whether before or after, the feast of Saint Andrew the Apostle, November 30. Here we see an example of something very important. The Proper of the Season is always superior to the Proper of the Saints.
Following this are the four weeks of Advent and the Christmas festival which lasts from December 25 through the Feast of the Epiphany on January 6.
The Sundays that follow are called the first, the second, the third, and so forth, after Epiphany. (Note: Unlike post-conciliar Catholics, Traditional Catholics will argue that no time on the Church calendar should be called Ordinary Time, which was an invention of Vatican II periti. On the contrary, all time with God is a gift and special, so the term now used is considered by Traditionalist to be an insult to God. I mention this because I read a medieval three years ago that mentioned the time after Epiphany as Ordinary Time; the writer did poor research). The Sundays after Epiphany are never more than six in number, and their series, as a rule, is interrupted by the coming of Septuagesima Sunday, which is the ninth Sunday before Easter and the first of which in the liturgy is of a penitential character.
Septuagesima is followed by Sexagesima, and Quinquagesima (anybody remember their Latin numbers?); this last is the Sunday before Ash Wednesday, on which Lent begins. Lent has six Sundays; the last two are respectively, Passion Sunday and Palm Sunday. The week beginning with Palm Sunday – that in which Our Lord was betrayed and crucified – is known as Holy Week. The next important time is Easter Sunday, the feast of the Resurrection of Our Lord. The date of Easter depends upon the dates of which the preceding celebrations occur, and is the Sunday following the full moon first occurring after the twentieth day of the month of March. The earliest possible date for Easter is March 23, and the latest is April 25.
The weeks between Easter and Trinity Sunday are known as Paschal Time. Forty days after Easter is the Ascension of Our Lord, which always falls on a Thursday; ten days later, the seventh Sunday and fiftieth day after Easter, is the Feast of the Descent of the Holy Ghost, also known as Pentecost or Whit-Sunday. The next Sunday is Trinity Sunday. The Thursday following Holy Mother Church is The Feast of Corpus Christi, the festival of the Most Blessed Sacrament. (A feast added in the 12th century, but which has such a wonderful story behind it, that it is often called Little Christmas). An octave later (eight days), is the Feast of the Sacred Heart of Jesus and the day after the Feast of the Immaculate Heart of Mary. With this, the cycle of movable feasts ends.
The remaining Sundays of the year, which cannot number more than twenty-eight or less than twenty-three, are described as the third, fourth, etc. after Pentecost. Another major difference between the Traditional Roman Rite and the post-conciliar liturgy is the placement of the Feast of Christ the King. Traditionally, it is the last Sunday of October, because Traditionalists believe that after Our Blessed Lord comes again, we will live in a time of peace with Him on earth. The Novus Ordo (New Order) of the Mass places the Feast of Christ the King on the last Sunday before Advent. I’ve never heard a good reason for this move from a liturgical or theological perspective, but Denzinger very well supports the Traditional placement of the festival. Also, since I mentioned Denzinger, let me add that it is one of the best authorities on Roman Dogma, referenced by date and approving authority. It is somewhat expensive, but worth the price to anyone writing medieval.
Happy reading and writing!
Can a captive escape when love claims her heart?