This is the Fourth Sunday in Advent - and this year it is also the LAST DAY of Advent! Tomorrow is the Christ Mass! Joy to the world! Peace unto men of goodwill (not the mistranslation of "goodwill, peace to men").
Today marks the closing of the shortest possible Advent Season, and tomorrow starts the Christmas Season. The "Twelve Days of Christmas" start on December 25th, Christmas Day, and go through January 5th. January 6th begins Epiphany (which is also a Christmas Season). Christmas can actually be celebrated all the way to February 2nd which is Candlemas - and in the lectionary Candlemas is the last time for the liturgical year that the Nativity of our Lord is mentioned in the readings. So, don't be in too much of a hurry to take down your Christmas decorations!
Don't forget! While every Sunday is a holy day of obligation, so is tomorrow! The Christ Mass is one of the highest of all the feast days - second only to Easter Sunday. The way we explained this to our children when this happens is "You don't HAVE to go to Mass two days in a row, you GET to!"