The Roman Catholic liturgical season of Septuagesima marks the transition from the Christmas cycle to the Lenten cycle of the Church calendar. The season, named for the Sunday seventy days before Easter, also contains the next two Sundays before Lent proper. These additional Sundays, Sexagesima and Quinquagesima, set apart a "mini-Lent" -- that is, violet vestments are worn but without the veiling of images. The liturgical reforms of Vatican II removed Septuagesima, replacing the season with
Ordinary Time between Christmas and Lent to greater emphasize Lent's forty day symbolism. Tridentine Rite Catholics adhere to the old calendar, with little or no modification.
Septuagesima
While few are able to trace the name Septuagesima to a definitive source, some suggest that the term derives from the seventy year Israelite Babylonian captivity. Alternatively, some Christian communities may have begun their Lenten observance around the time of Septuagesima, accounting for the breviary's penitential Scripture readings and the suppression of the Gloria and Alleluia as in Lent. Many areas produced embellished sequences designed to send off the Alleluia until Easter. In the new Rite of Mass, the Alleluia and Gloria are retained until the First Sunday of Lent.
Sexagesima and Quinquagesima
Sexagesima and Quinquagesima (sixtieth and fiftieth day before Easter, respectively) ramp up towards Lenten penitential practices through appropriate readings, i.e. Noah's Flood as the response to sin. These two feasts mark the phasing in of fast and abstinence laws. Sexagesima roughly corresponds with the Greek and Slavic churches' abstention from meat, with a large number of Western Christians beginning abstention on Quinquagesima.
Shrovetide, with Shrove Tuesday, grew out of the final days of the Septuagesima cycle. Quinquagesima's rush to get meat items, particularly butter, out of the home gave rise to pancake breakfasts and flipping contests. The Shrovetide example illustrates the deep ruts liturgy weaves into societies, even through Septuagesima's diminished importance in post-Reformation England.
http://www.newadvent.org/cathen/13721b.htm
http://www.newadvent.org/cathen/12614a.htm
http://www.newadvent.org/cathen/13747a.htm