Septuagesima (in full, Septuagesima Sunday), an observance dropped from the calendar as revised by the Second Vatican Council but still in use in the traditional calendars, is the name given to the third from the last Sunday before Lent in the Catholic and Anglican churches. The Lutheran Church Year continues using the name. The term is sometimes applied to the period of the liturgical year which begins on this day and lasts through Shrove Tuesday (with the following day being Ash Wednesday, when Lent begins). This period is also known as the Pre-Lenten season or Shrovetide. The next two Sundays are labelled Sexagesima and Quinquagesima, the latter sometimes also called Shrove Sunday. The earliest Septuagesima Sunday can occur is January 18 (Easter falling on March 22 in nonleap year) and the latest is February 22 (Easter falling on April 25 in leap year).
Septuagesima comes from the Latin word for "seventieth," with Sexagesima and Quinquagesima equalling "sixtieth" and "fiftieth" respectively. They are patterned after the Latin word for the season of Lent, Quadragesima, which means "fortieth" because Lent is forty days long (not counting the Sundays, which are all considered little Easters). Because a week is only seven days long, not ten, and since even then only six of those days might be counted if the pattern of Quadragesima is followed, Septuagesima, Sexagesima, and Quinquagesima, obviously don't literally correspond to the periods of time they imply. Some have theorized, however, that Septuagesima may have been added to the liturgical calendar to commemorate the Babylonian Captivity, which lasted 70 years (there is evidence that some early Christians began fasting 70 days before Easter, but whether that custom originated from this is not entirely clear). It is interesting, however, that just about 70 days (68 actually) is the minimum number of days between the octave day of the Epiphany on January 14 and Easter, implying that a season just about 70 days long can always fit between the two.
The 17-day period beginning on Septuagesima Sunday was intended to be observed as a preparation for the season of Lent, which is itself a period of spiritual preparation (for Easter). In many countries, however, Septuagesima Sunday still marks the traditional start of the carnival season, culminating on Shrove Tuesday, more commonly known as Mardi Gras.
In the pre-1970 Roman Catholic liturgy, the Alleluia ceases to be said during the liturgy, effective at Compline on the Saturday before Septuagesima Sunday, not to be sung again until Easter. Likewise, violet vestments are worn, except on feasts, from Septuagesima Sunday until Holy Thursday. As during Advent and Lent, the Gloria and Te Deum are no longer said on Sundays. The readings at Matins for this week are the first few chapters of Genesis, telling of the creation of the world, of Adam and Eve, the fall of man and resulting expulsion from the Garden of Eden, and the story of Cain and Abel. In the following weeks before and during Lent, the readings continue to Noah, Abraham, Isaac, Jacob, and Moses. The Gospel reading for Septuagesima week is the parable of the Workers in the Vineyard (Matthew 20:1-16).
With the liturgical reforms adopted after the Second Vatican Council, Septuagesima, Sexagesima and Quinquagesima Sundays were dropped and the period encompassing them became part of Ordinary Time, and because of this, the use of violet vestments and omission of "Alleluia" in the liturgy do not start until Ash Wednesday. This took effect in 1970 in the Catholic Church and six years later the Anglican Churches. In the Anglican Churches these Sundays are now known as the three "Sundays before Lent."
A version of the season still does exist in the Eastern Orthodox liturgical calendar, and is known as Triódion (although it is only 15 days long and not 17 since the Eastern Orthodox Lent commences on a Monday instead of a Wednesday).