Well, I would say they are both penitential but to different degrees. Advent
used to be penitential to a greater degree, but it appears to me (I wasnât around back then so I canât be sure) that its character was changed following Vatican II:
The liturgical year is to be revised so that the traditional customs and discipline of the sacred seasons shall be preserved or restored to suit the conditions of modern times; their specific character is to be retained, so that they duly nourish the piety of the faithful who celebrate the mysteries of Christian redemption, and above all the paschal mystery. (
Sacrosanctum Concilium 107)
For example, Pope Pius XII writes the following of Advent and Lent in
Mediator Dei of 1947:
154. In the period of Advent, for instance, the Church arouses in us the
consciousness of the sins we have had the misfortune to commit, and urges us, by
restraining our desires and
practicing voluntary mortification of the body, to
recollect ourselves in meditation, and
experience a longing desire to return to God who alone can free us by His grace from the stain of sin and from its evil consequences.
- During the days of Septuagesima and Lent, our Holy Mother the Church over and over again strives to make each of us seriously consider our misery, so that we may be urged to a practical emendation of our lives, detest our sins heartily and expiate them by prayer and penance. For constant prayer and penance done for past sins obtain for us divine help, without which every work of ours is useless and unavailing.
It would appear that fasting used to be a part of Advent in the Western Church; it is still in the Eastern Church (where it is called âPhilipâs Fastâ). See here for more details on Advent fasting.
Nowadays, Advent and Lent are still
somewhat similar in character. Consider the following liturgical prescriptions:
[The Gloria] is sung or said on Sundays
outside the Seasons of Advent and Lent. (GIRM 53)
During
Advent the
floral decoration of the altar should be
marked by a moderation suited to the character of this season, without expressing prematurely the full joy of the Nativity of the Lord. During
Lent it is
forbidden for the altar to be decorated with flowers. Laetare Sunday (Fourth Sunday of Lent), Solemnities, and Feasts are exceptions. (GIRM 305)
In
Advent the
organ and other musical instruments should be
used with a moderation that is consistent with the seasonâs character and does not anticipate the full joy of the Nativity of the Lord. In
Lent the playing of the organ and musical instruments is
allowed only to support the singing. Exceptions are Laetare Sunday (Fourth Sunday of Lent), Solemnities, and Feasts. (GIRM 313)
Violet or purple is used in Advent and Lent. ⌠Rose may be used, where it is the practice, on Gaudete Sunday (Third Sunday of Advent) and on Laetare Sunday (Fourth Sunday of Lent). (GIRM 346)
When a marriage is celebrated during
Advent or Lent or other days of penance, the parish priest should advise the couple to take into consideration the special nature of these liturgical seasons. (Rite of Marriage 11)
This blog post is provides a helpful history of Advent; here are two quotes found in the post:
âAdvent was not considered a penitential season till about the XIIIth century. In the XIIth century it was still kept with white vestments and the Gloria. The omission of the Gloira in Lent and Advent is natural enough from its joyful character.â
âThere is yet one more item of our present Roman Advent which we must trace to the Gallican tradition: its penitential character. According to the liturgical books of the early Middle Ages the Roman Advent was not a penitential season. It was simply a period of preparation for, and a joyful expectation of, Christmas. Therefore only the Sundays had the special characteristics of Advent. It was not until after the tenth century, when the Gallic Advent had exerted its influence on the Roman Advent, that it received its present penitental character. Now, however, the Gloria [is] omitted on the Sundays in Advent, purple vestments are worn just as in Lent, and a restriction is placed on the use of flowers and the organ. However, it never became - except in passing - a period of fasting. These are the influences of the old Gallic liturgy, of the ancient quadragesima S. Martini, on the Roman liturgy; it gave to our Advent and to our preparation for Christmas its more serious character.â
Jimmy Akin also addressed the penitential character of Advent.