While the secular calendar year begins on January 1 and ends on December 31, and the fiscal year in most places starts on July 1, the Church calendar or Liturgical Year is completely different.
Beginning on the first Sunday of Advent and ending on the Solemnity of Christ the King, the Church calendar does not have a fixed numerical date like the other two calendars. The first Sunday of Advent can fall on a day in November or in December. The only requisite is that it is four Sundays before Christmas since there are the second, third, and fourth Sundays of Advent before Christmas (which is always December 25).
The Liturgical Year refers to the designation of each Sunday as being part of a liturgical season, which reflects the cycles of life on earth and salvation history as well. Christmas and Easter are the two focal points of the Church year. The first centers on the theme of Christ our light, and the second focuses on the theme of Christ our life. Advent precedes Christmas and Lent precedes Easter. Ordinary Time occurs between these two major celebrations of the birth and death and resurrection of the Savior; all the Sundays and weekdays which have no proper celebration fall into the category called Ordinary Time.
Advent and Christmas occur in winter when there is less daylight than in the summer. During these two liturgical seasons—one preparing for Advent and one celebrating the birth of Christ—the readings and prayers recall the theme of Christ as “Light of the World,” in contrast to the lack of daylight which is quite evident during this time.
Lent and Easter occur in the spring when the snow has melted; nature wakes up from its nap, and we see flowers and animals exhibiting life after the long death of winter. These two liturgical seasons center on the theme of Christ as “Life of the World,” especially after His own Resurrection from the dead on Easter Sunday.
The preparation times of Advent and Lent are penitential; people pray more and engage in personal mortification, fasting, abstinence, and the like. The liturgical color for vestments for both Advent and Lent is purple or violet. Christmas and Easter, the pinnacles of the year, are the major celebrations, hence there is no fasting or abstinence and white is the proper liturgical color for vestments. Formerly the last Sunday in October and now the Sunday before Advent, Christ the King is the closing day of the Liturgical Year, since the following weekend is the first Sunday of Advent.
There are also Divine Solemnities like Ascension Thursday (forty days after Easter when Jesus ascended to heaven), Pentecost Sunday (fifty days after Easter when the Holy Spirit came upon the apostles), Trinity Sunday, Corpus Christi, Sacred Heart of Jesus, and other solemnities of the Virgin Mary like the Immaculate Conception (when Mary was conceived without original sin in the womb of her mother, Saint Ann) and the Assumption (when Mary was taken up to heaven body and soul by her son, Jesus).