What Happened to the Penance?  

In the sixth century Irish missionaries used Advent as a time to emphasize the last judgment. Thus Advent became a penitential season with fasting, prayer, and purple vestments—in other words, another Lent.  In Rome in that same century, under Pope Gregory the Great, Advent focused on the Incarnation during the four weeks before Christmas. By the time the Roman liturgy took its present shape we were into the eleventh century. The Church borrowed elements from its three main types of “Advents” in previous centuries. While retaining purple vestments, Advent became primarily a season of joyful expectation.