Gaudate in Domino semper! Rejoice in the Lord always!
Advent originated as a forty day preparation for Christmas but was eventually shortened to 4 weeks. Since the origin of this preparation was originally penitential in character the Church offered the third Sunday as a break from the otherwise disciplined thread of what Advent hoped to inspire for all the Christian faithful. In fact, the entire Advent season has become more of a festive season and has moved away from an explicitly disciplined season in which a fast was called for, beginning the day after St. Martin’s Feast (November 12th).