The Christmas season immediately follows Advent. The traditional Twelve Days of Christmas begin with Christmas Eve on the evening of December 24 and continue until the feast of Epiphany. The actual Christmas season continues until the Feast of the Baptism of Christ, which in the present form of the Roman Rite is celebrated on the Sunday after January 6, or the following Monday if that Sunday is Epiphany.
when does the liturgical season of christmas start
December 24