While not celebrated much any more today is the Saints Day of Knut in Sweden and Norway. This used to be considered the end of the Christmas season in these countries and would be the day when the tree was taken down and the cookies and candies on the tree eaten.
Why would today be the end? Well, from what I can gather it is due to the change in from the Julian calendar to the Gregorian. Originally, (and I think officially by the churches recognizing) the 7th of January was St. Knut's Day. This is the day after the Epiphany, the official end of Christmas. So while you would celebrate until the last day the day after would be the day to take down all the decorations. This tradition stuck when the calendar changed. I did find a really good write up on a lot of the holiday here (if you are interesed in reading more take a look, very interesting write up) and she does not seem to have found the change in the calendars to be the cause or does not agree with it, not sure which.
Links: http://en.wikipedia.org/wiki/St._Knut%27s_Day