Why does Lent begin on Ash Wednesday?

Lent is a preparatory season which Catholics use to prepare their souls for the solemnity of our Lord's Passion, suffering and death and His Glorious resurrection at Easter. It is the most important celebration of the liturgical year as it defines the very meaning of the central teaching of Christianity: that Christ died on a cross to save us from our sins and to lead us into Eternal Life with God. Ash Wednesday marks the beginning of this season.