In the traditional Roman Catholic calendar, the one in place until Advent 1969, the three Sundays before Lent were a period of preparation for the season of fasting, abstinence, almsgiving, and prayer. (See Ramping Up for Lent for more details.)
The names of those Sundays, however, were always a bit confusing. The third Sunday before Ash Wednesday was called Septuagesima Sunday, from the Latin word for 70; the second Sunday was known as Sexagesima, from the Latin word for 60; and the final Sunday before Ash Wednesday was called Quinquagesima, from the Latin word for 50. The 70, 60, and 50 refer to the number of days until Easter.
But if the Sundays are all (by definition) seven days apart, how can they be 70, 60, and 50 days from Easter, respectively? The quick answer is that they can't. The long answer is a bit more interesting.
As hard as it is to believe that words as lengthy as Septuagesima, Sexagesima, and Quinquagesima could be abbreviations, that is exactly what they are. The full and proper name of each Sunday is Dominica in Septuagesima, Dominica in Sexagesima, and Dominica in Quinquagesima. Dominica is the Latin word for Sunday (the Lord's Day), and so the full title for Septuagesima (for instance) means "Sunday in the 70 days" before Easter.
We're now in the period of Sexagesima, the 60 days before Easter, and perhaps I'm showing my age, but every year on Sexagesima Sunday, I wake up with these words running through my mind: "T minus 60 and counting." For those who remember the U.S. space program, the words will seem familiar, because they marked the final minute of the countdown before the rocket or shuttle blasted off for space.
For us as Catholics, those words can represent something more sublime, when combined with this Sunday of Sexagesima. We have not yet begun Lent, but we can see the end of this period of preparation on the horizon, and that end is salvation itself, in the Resurrection of Jesus Christ on Easter Sunday.
So as we prepare ourselves to enter Lent, so that we can prepare ourselves for Easter, let the countdown begin!