The liturgical season of Christmas starts on December 25 and lasts through January.
However, in the Roman Catholic Church, the liturgical season of Christmas does not start until December 25 (including the vigil celebrated on December 24) and lasts through January.
The USCCB explains how, “The liturgical season of Christmas begins with the vigil Masses on Christmas Eve and concludes on the Feast of the Baptism of the Lord. During this season, we celebrate the birth of Christ into our world and into our hearts, and reflect on the gift of salvation that is born with him…including the fact that he was born to die for us.”
This is where it can get a little more confusing as the Baptism of the Lord is a moveable feast, depending on the day when Epiphany falls in the Roman calendar.
For those dioceses that celebrate Epiphany on January 6, the Baptism of the Lord falls on the Sunday after it. In other places where Epiphany is celebrated on the first Sunday that falls from January 2 through January 8, then the Baptism of the Lord could occur either on the following Sunday, or on a Monday (this happens if Epiphany is celebrated on January 7 or 8).
The latest that the Baptism of the Lord can occur is January 13. Ordinary Time starts on the day after this feast.
This means that during certain years, Christmas lasts from December 25 – January 13!
If you want to celebrate the historical Christmas cycle, it extends even past the Baptism of the Lord. Traditionally the feast of Candlemas (the Presentation of the Lord) occurs on February 2 and marked the final conclusion of the Christmas cycle.
This is because Candlemas celebrates an event that occurred 40 days after Jesus’ birth and was his first introduction to the Temple. In other words, it is the final “baby Jesus” feast day on the Church’s liturgical calendar.
In some places people did keep up Christmas decorations like the creche until February 2, though it is probably not advisable to keep your Christmas tree up for that long (it may be a fire hazard at that point).
Technically speaking, if you truly want to celebrate Christmas like Christians in ages past, you wouldn’t decorate the house until Christmas Eve and then keep everything up until February 2.
This is very different from Christmas celebrations today!