Just as a typical calendar has four seasons, twelve months, fifty-two weeks, and 365 days that include holidays, solemn days, commemorative days, and days that are just "average," the Liturgical Year Calendar of the Church uses similar terms and measurements.
The Liturgical Year is also marked by special seasons—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.
However, the purpose of the Liturgical Year Calendar is not to mark the passage of time, but to celebrate and understand more fully the entire mystery of Jesus Christ, from his incarnation and birth until his ascension, the day of Pentecost, and the expectation of his return in glory. During the course of a year, the paschal mystery—the passion, death, resurrection, and ascension of Jesus—is viewed from different angles, in different lights.
The Liturgical Year Calendar first tells us what readings the Church has designated to be used for each day. Then it names the special feasts and commemorations celebrated during each season. These are listed one week at a time. A small colored cross reflects the color of the vestments to be worn by the priest during each celebration of the liturgy.
Liturgies celebrated during the different seasons of the liturgical year have distinctive music and specific readings, prayers, and rituals. All of these work together to reflect the spirit of the particular season. The colors of the vestments that the priest wears during the liturgy also help express the character of the mysteries being celebrated.
White, the color of joy and victory, is used for the seasons of Easter and Christmas. It is also used for the feasts of Our Lord, for feasts of Mary, the angels, and for saints who are not martyrs. Gold may also be used on solemn occasions.
Red (the color of blood) is used on days when we celebrate the passion of Jesus on Passion Sunday and Good Friday. It is also used for the birthday feasts of the apostles and evangelists and for the celebrations of martyrs. Red (the color of fire) recalls the Holy Spirit and is used on Pentecost and for the sacrament of Confirmation.
Green, seen everywhere in plants and trees, symbolizes life and hope and is used during Ordinary Time.
The colors violet or purple in Advent help us to remember that we are preparing for the coming of Christ. Lent, the season of penance and renewal, also uses the colors violet or purple.
Rose may be used on the Third Sunday of Advent, Gaudete Sunday, and on the Fourth Sunday of Lent, Laetare Sunday. It expresses the joy of anticipation for Christmas and Easter, respectively.