The ability to recall, and sing a cappella, all verses of the carol "Good King Wenceslas" is my most annoying party trick --- and I've not pulled it out of my hat yet this year, so be warned. It used to be especially satisfying to do this on a busy evening at the office, when it was particularly aggravating. Improvisation has been called for since.
This would be the day to do it --- the feast day of St. Stephen, Martyr, an early deacon stoned to death, as Paul tells us in Acts of the Apostles, for blasphemy after telling off the authorities.
The 19th century carol is a retelling of legends surrounding Wenceslas I, ca. 907-935, a man of legendary goodness reportedly assassinated by his brother (Boleslav the Cruel), and patron saint of the Czech state, where "Wenceslas" is "Vaclav." The good king and his page set out through the cold and snow with meat and wine and firewood to aid a peasant on the feast day of St. Stephen.
I have this issue with Christmas --- just get interested about the time others are losing steam. Which is why the 12 days of Christmas, commencing on Christmas day, are so useful. Maybe by the eve of the Epiphany, I'll have the tree decorated.