Throughout most of Christian history, if you asked any Catholic how long the Lenten fast was, he would have replied, without hesitation, “40 days.”

In recent years, however, a number of different answers have begun to appear, often spread by well-meaning Catholic apologists who have come to mistaken conclusions by examining current Church documents without consideration of the historical development of the Lenten fast, and the difference between Lent as a penitential season and Lent as a liturgical season.

• The relatively recent development of the Easter Triduum as its own liturgical season has not affected the length of the Lenten fast;
• The Lenten fast has been, and remains, exactly 40 days;
• The Sundays in Lent have never been, and still are not, part of the Lenten fast.

Until very recently, the liturgical season of Lent and the Lenten fast were coextensive, running from Ash Wednesday until Holy Saturday, when the Easter season began at the start of the Easter Vigil. With the revision of the rites of Holy Week in 1956, however, a new liturgical emphasis was placed on the Triduum, understood at that time as encompassing Holy Thursday, Good Friday, and Holy Saturday.

With the revision of the calendar in 1969, the Triduum was extended to include Easter Sunday as well, and the General Norms for the Liturgical Year and the Calendar issued by the Sacred Congregation of Divine Worship offer this definition of the Easter Triduum (para. 19):

The Easter triduum begins with the evening Mass of the Lord’s Supper, reaches its high point in the Easter Vigil, and closes with Evening Prayer on Easter Sunday.

Lent runs from Ash Wednesday until the Mass of the Lord’s Supper exclusive.

This redefinition of the Lenten liturgical season has led some to conclude that Lent is 43 days long, counting all of the days from Ash Wednesday to Spy Wednesday, inclusive; or 44 days long, if we include Holy Thursday, since the Mass of the Lord’s Supper begins after sundown on Holy Thursday.

And if we’re speaking of the liturgical season as currently defined by the Church, either 43 or 44 days is a reasonable answer for the length of Lent. But neither answer is correct if we are speaking of the Lenten fast.The 40 Days of the Lenten Fast

The current Catechism of the Catholic Church (para. 540) states:

The 40 days mentioned here are not figurative or approximate; they are not a metaphor; they are literal. They are tied, as the 40 days of Lent have always been for Christians, to the 40 days that Christ spent in fasting in the desert after His baptism by John the Baptist. Paragraphs 538-540 of the current Catechism of the Catholic Church speak of the “salvific meaning of this mysterious event,” in which Jesus is revealed as “the new Adam who remained faithful just where the first Adam had given in to temptation.”

By uniting “herself each year to the mystery of Jesus in the desert,” the Church participates directly in this salvific act. It’s no wonder, then, that from a very early period in the Church’s history, a literal 40 days of fasting has been seen as necessary by Christians.

The History of the Lenten Fast

In the language of the Church, Lent has historically been known by the Latin term Quadragesima—literally, 40. These 40 days of preparation for the Resurrection of Christ on Easter Sunday were, again, not approximate or metaphorical but literal, and taken very seriously as so by the entire Christian Church from the days of the Apostles. As the great liturgical scholar Dom Prosper Guéranger writes in Volume Five of his masterwork The Liturgical Year,

Over time, however, differences arose over how the 40 days of fasting were to be observed—though never of the necessity of 40 days of fasting. In Volume Four of The Liturgical Year, Dom Guéranger discusses Septuagesima, the traditional season of preparation for Lent, which originated in the Eastern Church:​

In the Western Church, however, the practice was different:

The Church of Rome had no such motive for anticipating the season of those privations, which belong to Lent; for, from the earliest antiquity, she kept the Saturdays of Lent, (and as often, during the rest of the year, as circumstances might require,) as fasting days. At the close of the 6th century, St. Gregory the Great, alludes, in one of his Homilies, to the fast of Lent being less than Forty Days, owing to the Sundays which come during that holy season. “There are,” he says, “from this Day (the first Sunday of Lent) to the joyous Feast of Easter, six Weeks, that is, forty-two days. As we do not fast on the six Sundays, there are but thirty-six fasting days; . . . which we offer to God as the tithe of our year.”

The importance of a literal 40-day period of fasting cannot be stressed enough; as Dom Guéranger writes,

There can be no doubt, but that the original motive for this anticipation,—which, after several modifications, was limited to the four days immediately preceding Lent,—was to remove from the Greeks the pretext of taking scandal at the Latins, who did not fast a full Forty days. . . .

Thus it was, that the Roman Church, by this anticipation of Lent by Four days, gave the exact number of Forty Days to the holy Season, which she had instituted in imitation of the Forty Days spent by our Saviour in the Desert.

And in that final sentence from Dom Guéranger, we see the continuity with the line quoted earlier from para. 540 of the current Catechism of the Catholic Church (“By the solemn forty days of Lent the Church unites herself each year to the mystery of Jesus in the desert.”), in the understanding of both the purpose and the length of the Lenten fast.

Sundays Are Not, and Never Have Been, Part of the Lenten Fast

If the Church, both East and West, considered it of paramount importance that the Lenten fast be exactly 40 days, why did the Western Church extend the Lenten fast back to Ash Wednesday, which falls 46 days before Easter? Dom Guéranger spells it out for us, in this excerpt from Volume Five of The Liturgical Year:

We have already seen, in our Septuagesima [Volume Four], that the Orientals begin their Lent much earlier than the Latins, owing to their custom of never fasting on Saturdays, (or, in some places, even on Thursdays). They are, consequently, obliged, in order to make up the forty days, to begin the Lenten Fast on the Monday preceding our Sexagesima Sunday. These are the kind of exceptions, which prove the rule. We have also shown, how the Latin Church,—which, even so late as the 6th Century, kept only thirty-six fasting days during the six weeks of Lent, (for the Church has never allowed Sundays to be kept as days of fast,)—thought proper to add, later on, the last four days of Quinquagesima, in order that her Lent might contain exactly Forty Days of Fast.

“[F]or the Church has never allowed Sundays to be kept as days of fast . . . ” Thus, we arrive at the traditional formula, in the Western Church, for how the 40 days of Lent are calculated

• Ash Wednesday to Holy Saturday, inclusive, is 46 days;
• There are six Sundays in this period, which “the Church has never allowed . . . to be kept as days of fast”;
• 46 days minus 6 Sundays equals the 40 days of the Lenten fast.

The Church continues today to regard every Sunday as a “little Easter.” As the Church’s 1983 Code of Canon Law notes (Canon 1246):

Sunday, on which by apostolic tradition the paschal mystery is celebrated, must be observed in the universal Church as the primordial holy day of obligation.

(This is why, by the way, Easter and Pentecost, as important as they are, are never listed as separate holy days of obligation: Both fall on Sunday, and all Sundays are holy days of obligation.)

All holy days of obligation, or solemnities, have an exalted status in the Church. They are days on which penitential obligations, such as our obligation to abstain from meat on Fridays, are lifted, as Canon 1251 notes (emphasis added):

Abstinence from meat, or from some other food as determined by the Episcopal Conference, is to be observed on all Fridays, unless a solemnity should fall on a Friday.

The continuous tradition of the Church, East and West, applies today, both during Lent and throughout the year: Sundays are not days of fasting. Any sacrifice that we make as part of our observance of the 40-day Lenten fast is not binding on the Sundays of Lent, because the Sundays of Lent are not, and never have been, part of the Lenten fast.