The season of Lent begins on Ash Wednesday (this year this is on March 5). Lent is a time of preparation for the great feast of Easter, when we celebrate Jesus' resurrection from the grave.
Before we get to Lent we observe the "Pre-Lenten" season, consisting of 3 Sundays each of which has a strange sounding Latin name. This past Sunday (Feb 16) was Septuagesima, next Sunday (Feb 23) is Sexagesima and the final Sunday in the pre-lenten season is Quinquagesima (March 2). These Sundays are so named to indicate the (approximate) number of days left before Easter - 70, 60 and 50 respectively. (On Ash Wednesday there are 40 left until Easter, not including Sundays).
Each of the Pre-Lenten Sundays has a different emphasis (the following is taken from a very helpful note written by Bishop Paul Hewett):
Septuagesima Sunday: by God’s grace we are called to work with Him in His vineyard, to live with Him in His Kingdom, to run the race, on His team.
Sexagesima Sunday: the harvest of the vineyard, the rewards of the Kingdom, are assured. Our labor is not in vain, we are not wasting our time.
Quinquagesima Sunday: the fruits of our work in the Kingdom are to grow in our capacity to love God, and our neighbor, in God.
