The Feast is also called, Feast of the Purification (Candlemas) 40 days after giving birth, Mary goes to the Temple to be purified and to "redeem" Jesus per the Old Testament Law of the firstborn. Christmas truly ends as a Season with Candlemas and the beginning of Septuagesima.
Abbot Gabriel, St. Benedict's Abbey, Still River, MA, talked about this in his Homily yesterday. I decided to look it up on-line, I believed him but I know some of you would like to see the official word. I found the most infomation on a traditional Catholic webstie, http://www.fisheaters.com/customschristmas1.html. Check it out if you are interested. I know I was.