January 6 is known in the Christian calendar as Epiphany. It signifies the event of the Magi, or Wise Men visiting the baby Jesus, and is known in certain Latin cultures as Three Kings Day. In the Eastern (Orthodox and Oriental) churches it is known as the Feast of Theophany (God Manifest), commemorating Jesus’ baptism — recounted in all four Gospels of the New Testament — with the attendant appearance of the Holy Spirit as a dove and the voice of God the Father. This date is also tied to Jesus’ miracle of changing the water to wine at the Wedding of Cana in the Gospel of John Chapter 2.
So, the 12 Days of Christmas don’t end at Christmas, Advent does. Instead, the 12 days start with Christmas, and end with Epiphany, these 12 days sometimes called Christmastide. The subsequent “season” of Epiphany lasts from January 6 through the day before Lent. Some Latin American and European cultures extend this season to February 2, or Candlemas.