Why does the Christmas season end on the feast of the Baptism of the Lord?
In the early centuries, the birth of Christ didn’t have its own feast. It was part of a great feast on January 6 called “Epiphany” which celebrated several “manifestations” of Christ – his birth, his recognition by the Magi, his baptism in the Jordan, and his miracle at Cana.
In about the fourth century, Christians in the western world pulled Christmas out of the Epiphany celebration and have it a feast of its own on December 25. The time between this feast on December 25, and the feast on January 6 became the Christmas season – the “12 days of Christmas.”
But the Christmas season no longer ends on January 6. That’s because eventually, some parts of the Church made the feast of Epiphany more solemn by adding an “octave” – an extension of the celebration for a week after the feast.
When this happened, the Christmas season no longer ended on Epiphany but continued through the octave. The feast of the Baptism of the Lord was eventually placed at the end of the octave… and now that is the feast that brings the Christmas season to a close.