The Liturgical Year is marked by the special seasons of Advent, Christmas, Lent, the Triduum (or Three Days), Easter, and Ordinary Time. The Liturgical Year begins on the first Sunday of Advent, which usually occurs around the beginning of December or the end of November, and ends on the feast of Christ the King. The Liturgical Year Calendar tells us what readings the Church has designated to be used for each day. It also names the special feasts and commemorations celebrated during each season and marks the dates of remembrance of the saints.
(from the FDLC)
(calendar image courtesy of LTP)