Several years ago Loreto Publications printed the multi-volume The Liturgical Year by Dom Gueranger. This is still the most complete study of the Catholic liturgy but it is unfortunately out of print. Fortunately, I bought a copy and since it is not under copyright, I am going to be posting sections of it throughout the year.
It is important to note that this series was written for the Extraordinary Form calendar and liturgy so it will not match up with the Ordinary Form feasts and prayers. Still, the value of this exhaustive work makes it a wonderful reference and devotional regardless of what liturgy you attend.
Chapter the First
The History of Advent
The name Advent  is applied, in the Latin Church, to that period of the year, during which the Church requires the faithful to prepare for the celebration of the feast of Christmas the anniversary of the birth of Jesus Christ. the mystery of that great day had every right to the honour of being prepared for by prayer and works of penance; and, in fact, it is impossible to state, with any certainty, when this season of preparation (which had long been observed before receiving its present name of Advent) was first instituted. It would seem, however, that its observance first began in the west, since it is evident that Advent could not have been looked on as a preparation for the feast of Christmas, until that feast was definitively fixed to the twenty-fifth of December; which was done in the east only towards the close of the fourth century; whereas it is certain that the Church of Rome kept the feast on that day at a much earlier period.
We must look upon Advent in two different lights: first, as a time of preparation, properly so called, for the birth of our Saviour, by works of penance; and secondly, as a series of ecclesiastical Offices drawn up for the same purpose. We find, as far back as the fifth century, the custom of giving exhortations to the people in order to prepare them for the feast of Christmas. We have two sermons of Saint Maximus of Turin on this subject, not to speak of several others which were formerly attributed to St. Ambrose and St. Augustine, but which were probably written by St. Cesarius of Arles. If these documents do not tell us what was the duration and what the exercises of this holy season, they at least show us how ancient was the practice of distinguishing the time of Advent by special sermons. Saint Ivo of Chartres, St. Bernard, and several other doctors of the eleventh and twelfth centuries, have left us set sermons de Adventu Domini, quite distinct from their Sunday homilies on the Gospels of that season. In the capitularia of Charles the Bald, in 846, the bishops admonish that prince not to call them away from their Churches during Lent or Advent, under pretext of affairs of the State or the necessities of war, seeing that they have special duties to fulfil, and particularly that of preaching during those sacred times.
More to follow....