Q. Why is Ash Wednesday 40 days before Easter? What is the significance of the number 40? I know that it is used many times in the Bible (for example, Jesus was in the desert 40 days and 40 nights). How do you determine the date of Ash Wednesday? And where does the word Lent come from?
A. Some biblical writers regarded 40 years as the length of a generation. Thus, the Hebrews wandered in the wilderness for 40 years between leaving Egypt and entering the Promised Land, long enough for everyone in the original group—except Joshua and Caleb (Numbers 26:65)—to die off.
Because the early Christians regarded Moses’ parting of the sea as an Old Testament antecedent for Baptism and because Moses spent 40 days and 40 nights on Mount Sinai before encountering God, Christians used the number 40 as the length of the season to prepare catechumens for receiving the Sacrament of Baptism at the Easter Vigil.
The date of Ash Wednesday is counted back from the date of Easter (first Sunday after the first full moon after the spring equinox—March 21/22). Once you know the date of Easter, you count back six Sundays and then go to the previous Wednesday. That is Ash Wednesday; those six Sundays are not counted as part of the 40 days.
Lent comes from the Middle English lente (springtime). North of the equator, Lent roughly corresponds to spring.