The Modern Catholic Dictionary’s definition of Lent includes the following: “Originally the period of fasting in preparation for Easter did not, as a rule, exceed two or three days. But by the time of the Council of Nicaea (AD 325) forty days were already customary. And ever since, this length of time has been associated with Christ’s forty-day fast in the desert before beginning his public life.”
One interesting theory that has been written about by some theologians is that God’s original plan did not include the creation of humans. Instead, His original intention was to populate heaven with angels. Unfortunately, because of the pride and rebellion of Lucifer and his followers, a conflict arose and Lucifer and his followers were subsequently cast into hell. According to the theory, it was at that time that God decided to create the human race, with the intention of populating heaven with the exact number of humans needed to replace the fallen angels. Although it’s an interesting theory, we have no way of knowing whether it’s true.