"The "Twelve Days of Christmas" refer to the eight days of the Christmas Octave from December 25 to New Years Day, and the four additional days up to and including the eve of January 6, the traditional date of the Epiphany. In the USA and many other countries, Epiphany is now celebrated on the first Sunday after New Years, so the exact number 12 does not necessarily apply. But the point is, don't throw out the tree on the 26th--the birth of the Savior can't be celebrated adequately in one day. Let the celebration continue through at least through the Feast of the Epiphany--if not through the Feast of the Baptism of the Lord."
-Taken from The Crossroads Initiative, a Ministry of Dr. Marcellino D'Ambrosio