Lent is a special time of prayer, penance, sacrifice and good works in preparation of the celebration of Easter. In the desire to renew the liturgical practices of the Church, The Constitution on the Sacred Liturgy of Vatican Council II stated, "The two elements which are especially characteristic of Lent — the recalling of baptism or the preparation for it, and penance — should be given greater emphasis in the liturgy and in liturgical catechesis. It is by means of them that the Church prepares the faithful for the celebration of Easter, while they hear God's word more frequently and devote more time to prayer" (no. 109). The word Lent itself is derived from the Anglo-Saxon words lencten, meaning "Spring," and lenctentid, which literally means not only "Springtide" but also was the word for "March," the month in which the majority of Lent falls.

Since the earliest times of the Church, there is evidence of some kind of Lenten preparation for Easter. For instance, St. Irenaeus (d. 203) wrote to Pope St. Victor I, commenting on the celebration of Easter and the differences between practices in the East and the West: "The dispute is not only about the day, but also about the actual character of the fast. Some think that they ought to fast for one day, some for two, others for still more; some make their 'day' last 40 hours on end. Such variation in the observance did not originate in our own day, but very much earlier, in the time of our forefathers" (Eusebius, History of the Church, V, 24). When Rufinus translated this passage from Greek into Latin, the punctuation made between "40" and "hours" made the meaning to appear to be "40 days, twenty-four hours a day." The importance of the passage, nevertheless, remains that since the time of "our forefathers" — always an expression for the apostles — a 40-day period of Lenten preparation existed. However, the actual practices and duration of Lent were still not homogenous throughout the Church.

Lent becomes more regularized after the legalization of Christianity in A.D. 313. The Council of Nicea (325), in its disciplinary canons, noted that two provincial synods should be held each year, "one before the 40 days of Lent." St. Athanasius (d. 373) in this "Festal Letters" implored his congregation to make a 40-day fast prior to the more intense fasting of Holy Week. St. Cyril of Jerusalem (d. 386) in his Catechectical Lectures, which are the paradigm for our current RCIA programs, had 18 pre-baptismal instructions given to the catechumens during Lent. St. Cyril of Alexandria (d. 444) in his series of "Festal Letters" also noted the practices and duration of Lent, emphasizing the 40-day period of fasting. Finally, Pope St. Leo (d. 461) preached that the faithful must "fulfill with their fasts the Apostolic institution of the 40 days," again noting the apostolic origins of Lent. One can safely conclude that by the end of the fourth century, the 40-day period of Easter preparation known as Lent existed, and that prayer and fasting constituted its primary spiritual exercises.

Of course, the number "40" has always had special spiritual significance regarding preparation. On Mount Sinai, preparing to receive the Ten Commandments, "Moses stayed there with the Lord for 40 days and 40 nights, without eating any food or drinking any water" (Ex 34:28). Elijah walked "40 days and 40 nights" to the mountain of the Lord, Mount Horeb (another name for Sinai) (I Kgs 19:8). Most importantly, Jesus fasted and prayed for "40 days and 40 nights" in the desert before He began His public ministry (Mt 4:2).

Once the 40 days of Lent were established, the next development concerned how much fasting was to be done. In Jerusalem, for instance, people fasted for 40 days, Monday through Friday, but not on Saturday or Sunday, thereby making Lent last for eight weeks. In Rome and in the West, people fasted for six weeks, Monday through Saturday, thereby making Lent last for six weeks. Eventually, the practice prevailed of fasting for six days a week over the course of six weeks, and Ash Wednesday was instituted to bring the number of fast days before Easter to 40. The rules of fasting varied. First, some areas of the Church abstained from all forms of meat and animal products, while others made exceptions for food like fish. For example, Pope St. Gregory (d. 604), writing to St. Augustine of Canterbury, issued the following rule: "We abstain from flesh, meat, and from all things that come from flesh, as milk, cheese and eggs."