Greetings on the 14th Day of Christmas
The arrangement of Church year changed a lot after the Vatican Council II. The main change in the liturgical cycle after the council was the insertion of two periods of "ordinary time" into the year, which are assigned the liturgical color green. The pre-Lenten season called Shrovetide was dropped, and Ember days were removed, and these are just a few of the changes. The feasts in the two cycles still overlap in some cases (such as the great feasts of Advent, Christmas, Easter, and Pentecost), while some feasts in the new calendar are on different dates from the dates they were assigned on the traditional calendar (Christ the King Sunday for one example). In the new calendar, the Christmas season does not end until the Feast of the Baptism of Christ, which is usually on the Sunday after Epiphany. In the traditional calendar, the Christmas season continues until Candlemas in early February,
+ The dates of the feasts of the liturgical year change every year because Easter's date is moveable, based on the Vernal Equinox.
+ "Ordinary" comes from the same root as "ordinal", and Ordinary Time means "the counted weeks." The weeks in Ordinary Time are the weeks that do not belong to a proper season.
+ "Proper" in Church speak has a specialized meaning too. It means proper to the day or the season.
Sequence of Seasons in New Calendar
Thirty-three or thirty-four weeks of ordinary time are divided and inserted between the Christmas season and Lent and between Pentecost and Lent.
The first period of Ordinary Time in the liturgical year begins on Monday after the Sunday on which the Feast of The Baptism of Christ is celebrated, which is the Sunday following Epiphany on January 6. This part of ordinary time continues until the Tuesday before Ash Wednesday. This portion of Ordinary time lasts between 4 to 9 weeks depending on the dates of Epiphany and Ash Wednesday. The date of Ash Wednesday changes based on the moveable date of Easter.
The second period of Ordinary Time in the Liturgical year begins on the Monday after Pentecost and ends before Evening Prayer I of the First Sunday of Advent.
The Last Sunday before Advent is the Solemnity of Christ the King.
In some years, the number of weeks called Ordinary Time is actually 33. To keep the number at 34, in those years the Church adds a one to the number of the Sunday that follows Penetecost Sunday. For example, in 2008 the Sunday before Ash Wednesday was the 4th Sunday in Ordinary Time, but when Ordinary time started up again after Pentecost, that Monday began the 6th Week in Ordinary Time, and the next Sunday was the 7th Sunday in Ordinary Time. With that much happening in between the two periods of ordinary time, they must have figured, Who's going to notice?
Sequence of Seasons in Traditional Calendar
+ From Advent (Evening Prayer [EP] I of the First Sunday) to the Saturday before Septuagesima Sunday
The Circumcision of Jesus is celebrated eight days after Christmas, on January 1 (in the new calendar Our Lady's feast is celebrated on Jan. 1). January 6 is the Feast of the Epiphany. January 13 commemorates the Baptism of Jesus Christ and it marks the end of the Christmas season.
The period called the Time After Epiphany has between one and six Sundays, and it extends from January 14 until the start of the Easter Season on Septuagesima Sunday. The Time After Epiphany is shortened or lengthened depending on the variable date of Easter.
Septuagesima Sunday is the third from the last Sunday before Lent. It begins the Pre-Lenten season or Shrovetide. The following two Sundays are Sexagesima and Quinquagesima (aka Shrove Sunday). What the numbering (Septuagesima, Sexagesima, and Quinquagesima) means is interesting (but I don't have time to describe that right now). It is the time of preparation for Lent. Also marks the start of the carnival season, which in both forms ends on Shrove Tuesday, aka Fat Tuesday or Mardi Gras.
Alleluia, Gloria, and Te Deum stop being said beginning at Compline on the Sat. before Septuagesima Sunday and starts again at Easter. Violet vestments are worn.
* From the Sunday of Septuagesima (EP I on the Saturday before) too the Saturday before First Sunday in Advent
Septuagesima season is 17 days long and starts nine Sundays before Easter and ends the Tuesday before Ash Wednesday. During Septuagesima, as in Lent in both forms, the Alleluia and the Gloria are omitted, and violet vestments are worn.
Time After Pentecost has a minumum of 23 Sundays. If there are more, the Masss for the 23rd Sunday is said on the additional Sundays until Advent begines.
More on this topic according to the Roman Missal:
Easter being variable, the number of Sundays from Pentecost to the First Sunday of Advent is, of course, variable also; but there cannot be less than twenty-three not more than twenty-eight. The Mass for the last Sunday after Pentecost is always said on the Sunday preceding Advent. If there are more than twenty-four Sundays after Pentecost, the Introit, Gradual, and Communion of the twenty-third Sunday are repeated on all the remaining Sundays. But the Collects, the Epistle, and the Gospel are taken from the Masses of the Sundays omitted after the Epiphany. . ...