The liturgical year begins with the First Sunday of Advent, which usually occurs around the beginning of December or the end of November. The season of Advent continues through the four Sundays of Advent and ends at Christmas Eve. Advent, therefore, is firstly a time to prepare for Christmas. It is a season of waiting and anticipation of the birth of Jesus. Through the readings and environment, feelings of joy and excitement are evoked. Even though Christ was actually born over 2000 years ago, during Advent we prepare our hearts to "receive" Jesus into the world each year as a light to the nations, at a time when the regular calendar is reaching its darkest period. Advent is also a time of looking forward to Christ's Second Coming in the last days. It is a time of hope and eager expectation.
The Lectionary for Mass, which cycles through three liturgical years (A, B, and C), changes to a new year at Advent.
The third Sunday of Advent is called Gaudete Sunday. It takes its name from that Sunday's traditional reading from the Epistle to the Philippians (now read only in Year C) that begins with Gaudete in Domino semper ("Rejoice in the Lord always").
The liturgical color for Advent is violet, a deep bluish red (often mistakenly called "purple") symbolizing mourning and penance. On Gaudete Sunday, however, rose-colored vestments may be used for this joyful day. This also explains the one rose-colored candle among the other three violet candles of the Advent wreath.
On this celebration of the Incarnation, God enters the world to save us and bring us hope. The date on which the Church observes Christ’s birth is December 25. This date is mainly symbolic, falling five days (five being the number of the physical senses) after the winter solstice. Thus we celebrate the Word become flesh, coming to dwell among us as the light of the human race, just after the darkest point of the solar year. Christmas is a holy day second only to Easter in the Roman calendar.
The Octave of Christmas (octave means eight; hence the octave of Christmas lasts for eight days) begins with Christmas day and ends after the Solemnity of Mary, Mother of God (January 1st). Then the liturgical calendar focuses on the next immediate Sunday, counting off days before and after it, called Epiphany. Epiphany commemorates the recognition of Jesus as the Son of God by the three Wise Men (and by extension, by all pagan nations). The season of Christmas ends on the Monday after the Solemnity of the Baptism of the Lord, which signifies the purification of the world, through Christ himself.
By tradition, the movable feasts of the current liturgical year are announced to the people on Epiphany (Ceremonial of Bishops, 240).
The liturgical color of the season of Christmas is white, symbolizing purity and joy.
The season of Easter begins at the Easter Vigil. But before that, the week previous to Easter is called Holy Week; it begins with Passion Sunday (Palm Sunday). On Passion Sunday the Church celebrates Christ's riding into Jerusalem on a road strewn with cloaks and leafy branches (Mark 11:8; cf. Matthew 21:8, Luke 19:36, John 12:13), as he set about to accomplish his Paschal mystery. The week culminates with the Triduum (a Latin word for a three-day period) that includes Good Friday, Holy Saturday, and Easter itself.
The Triduum begins with the Evening Mass of the Lord's Supper on Holy Thursday. The next day, Good Friday, called “good” because on that day humanity was redeemed from its slavery to the powers of sin and death, is the most somber day of the liturgical year, for it commemorates Christ buried in his tomb. The tabernacle is empty, the altar is bare, statues of saints are removed from the church (or veiled), and the holy water fonts are dry-and no Mass is celebrated. The Good Friday liturgy begins with the proclamation of the Passion of Our Lord Jesus Christ according to John, continues with the veneration of the Cross and concludes with a simple Communion service with the Eucharist reserved from Holy Thursday's liturgy.
The Triduum culminates with the Easter Vigil on Holy Saturday, a liturgy that begins in total darkness until the Gloria returns with bells and Alleluias. Christ is risen!
The Easter season is considered such a special time that instead of continuing just for the eight days of the octave of Easter (all celebrated as solemnities of the Lord), it extends for 50 days (including Sundays and counting Easter Sunday itself). On Sundays during the Easter season, the assembly gathered for worship renews their baptismal promises and are sprinkled with holy water blessed at the Easter Vigil. These 50 days are to be seen as a single celebration of the central aspect of our lives as Christians that is the resurrection of the Lord. The season of Easter comes to a close, and Ordinary Time returns, on the Monday after Pentecost Sunday (from the Greek pentekoste, fiftieth day) on which we celebrate the descent of the Holy Spirit (Acts 2:1-13).
The liturgical color of the season of Easter is white, symbolizing purity and joy. Red, the color of passion, is used on Passion (Palm) Sunday and Good Friday. Red, symbolizing fire, is also used on Pentecost Sunday.
The liturgical season of Lent lasts for 40 weekdays in remembrance of the 40 days and nights that Christ spent fasting in the desert, tempted by Satan. The beginning of Lent, Ash Wednesday, is therefore dependent on the date of Easter.
Lent is a time of penance and preparation, so that the faithful may share in the joys of Easter Sunday with purity of heart. The three traditional forms of penance which are fasting, prayer, and almsgiving, "express conversion in relation to oneself, to God, and to others" (Catechism of the Catholic Church, 1434). For those adults preparing for Baptism at the Easter Vigil, Lent focuses on inner and outer scrutiny. For the baptized, Lent calls us to contemplate the redemption wrought for our sake by Christ's passion; and it admonishes us to contemplate the effort we put into accepting that redemption. In our Baptism, this redemption was planted in us when we promised to renounce sin and Satan and to live a chaste, holy life in devout service to Christ. Our salvation depends on our fulfilling those promises.
Because of the austerity of Lent, Alleluia is not said in prayer or sung in liturgy. The Gloria is not sung at Mass during Lent except for a few possible feasts and solemnities. During Lent, "the altar is not to be decorated with flowers, and the use of musical instruments is allowed only to support the singing" (Ceremonial of Bishops, 252).
The liturgical color of Lent is violet, just as for Advent. Rose-colored vestments, however, may be used on the Fourth Sunday of Lent, called Laetare Sunday from the first words of that day's Introit at Mass, Laetare Jerusalem ("Rejoice, O Jerusalem").
Two periods in the liturgical calendar are called Ordinary Time. The first period begins on the Monday after the Baptism of the Lord and continues until the Tuesday before Ash Wednesday (approximately 7 weeks). The second period begins on Monday after Pentecost and ends directly before the First Sunday of Advent, a lengthy period of about 30 weeks. Ordinary time is the longest season of the liturgical year.
This time is called "ordinary" because it is, simply, ordinary; that is, not part of any special liturgical season. However, the season of Ordinary Time has an important role to play in the liturgical calendar in that it connects the special seasons of the year and in our lives as Christians, as it reminds us that we are loved by God in the ordinary, daily moments of our lives. It is important to note that many feast days and solemnities occur in Ordinary Time: the Most Holy Trinity, the Most Holy Body and Blood of Christ, the Nativity of Saint John the Baptist, the Most Sacred Heart of Jesus, Saints Peter and Paul, the Assumption of the Blessed Virgin Mary, All Saints, and All Souls, for example.
The weekdays during Ordinary Time on which no solemnities, feasts, or memorials of saints fall are called ferial days. The liturgical color of Ordinary Time is green, symbolizing life and hope. The readings during this time do not have a specific theme or focus, as they do during the other seasons of the year. Emphasis and focus is placed on the lives of the saints and their model of holiness for us. The saints were indeed ordinary men and women who through grace became extraordinary witnesses of God’s presence