Through the liturgy the work of our redemption is exercised. It is â€œthe outstanding means by which the faithful can express in their lives, and manifest to others, the mystery of Christ and the real nature of the Churchâ€¦â€ (Constitution on the Liturgy,2). It is â€œthe summit toward which the activity of Church is directedâ€¦it is the fountain from which all her power followsâ€ (Liturgy 10).
On appointed days in the course of the year, the Church celebrates the memory of our redemption by Christ. Throughout the year the entire mystery of Christ is unfolded. She does this in sequence during the various seasons of the year.
This season beings four weeks (or slightly less) before Christmas. (The Sunday which falls on or closest to November 30 is its Starting point.)
This season lasts from Christmas until Sunday after Epiphany, or a after January 6, inclusive. The period from the end of Christmastide until the being of Lent belongs to the ordinary time of the year.)
The penitential season of Lent beings on Ash Wednesday and last until Easter. The last week is called Holy week, and its last three days are called as paschal Triduum.
The season, whose theme is resurrections from sin to the life of grace, lasts for 50 days, from Easter to Pentecost.
This season comprises the 33 or 34 weeks in the course of the year which celebrate no particular aspect of the mystery of Christ in all its fullness is of Christ, instead, the mystery of Christ in all its fullness is celebrated. It includes not only the period between the end of the Christmastide and the beginning of Lent but also all the Sundays after Pentecost to the last Sunday of liturgical year.