In order to grow in participation in the mystery of Christ the Church wisely arranges the liturgical year to cover all of the mighty acts of God. The possibility for contemplation of all of the stages of God’s salvific action in sacred history are there. The Church maintains the important link between God’s promise and His oath: from the promise of and subsequent longing for redemption in Advent; to the stupendous realization of God’s Word in the Incarnation; to the depths of His love in the events of Christ’s Pasch; to the establishment of His Mystical Body, the Church, on Good Friday and Pentecost. The "sacraments" of the Old Testament prefigure the sacramental order of the New Testament and the promises which precede Christ are all fulfilled in Him.
Even more important in the scheme of the liturgical year then the recounting of sacred history centered on Christological events is the prime mystery of the Trinity, wherein lies the birth of the plan for mankind: union with God in the Trinitarian family. There is one Sunday set aside for celebration of the Triune Godhead but in reality all of the feasts of the Church converge upon the feast of the Most Holy Trinity.
This central mystery of the Faith is always presupposed and so must always be freshly proposed, therefore the wisdom of the Church provides regular opportunities to reconsider it. In fact, each liturgical event which the Church celebrates has more and more depth to plumb. Dom Ghesquiere makes the following point:
The great stages of the history of salvation are outlined in the chain of their providential development: Israel, the Church on earth, the Church in Heaven. Facts speak, events answer one another, the mysterious links which God has willed are brought out by the conjunctions which in themselves are worth more than any commentary. 
Catechesis should carefully shape itself around the mysteries found in those events and remember that what is most crucial in the liturgical year is that the faithful are called to live the celebrations of the feasts. In Mediator Dei (no. 176) Pope Pius XII taught that:
... the liturgical year ...is no cold and lifeless presentation of past events, no mere historical record. It is Christ Himself, living on in His Church ... (The mysteries of His life) ... are still now consistently present and active ... (and are) sources of divine grace for us by reason of the merits and intercession of the Redeemer.
Preparation for these feasts is an integral factor in them not becoming "lifeless presentations of past events." These mysteries should "form the high points of biblical catechesis" according to Fr. Hofinger. He emphasizes that believers will experience the mysteries in the liturgy long before they may understand them. There they become "present religious values" and not just historical narratives.  In fact, it is often after the fact that at the practical level the liturgical year becomes a principal means by which the effects of the mystery of Christ are conveyed. It is a "magnificent unity" expressed in a "sublime manner," which plunges the believer directly into the heart of God’s plan.
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