In Catholicism, Christmastide begins with the celebration of the Nativity of the Lord on December 25th, known as Christmas Day. This festival marks the beginning of the Christmas season. Christmastide traditionally ends with the Feast of the Baptism of the Lord, which is celebrated on the Sunday following January 6th (Epiphany), or on January 13th if Epiphany is celebrated on January 6th. This feast marks the conclusion of the Christmas season in the liturgical calendar.