For the song about Beethoven's birthday featured in You're a Good Man, Charlie Brown, see Beethoven Day
Beethoven's birthday is the birthdate of Schroeder's idol, Ludwig van Beethoven. It is considered an important holiday by Schroeder. He first celebrated it in 1953, then celebrated it almost every year afterwards, on December 16.
Schroeder is the only person who really celebrates Beethoven's birthday, since he idolizes the composer. However, he has hosted parties that many people have gone to, as well as Lucy also celebrating it, but only to impress Schroeder. Normally, she is unable to impress him, and sometimes ends up hating Beethoven's birthday, since Schroeder does not care if Lucy likes Beethoven or not. However, in a strip from 1984, Schroeder kisses Lucy on the cheek because she gives him a cupcake. In a series of strips from November and December 1960, Lucy tries to commercialize the day, which makes Schroeder upset, because he wants people to enjoy Beethoven's birthday for Beethoven, and not for merchandise.
A running gag connected to Beethoven's birthday has Schroeder holding up signs to remind everyone that Beethoven's birthday is coming up. For instance, the sign says, "5 more days til Beethoven's birthday". In one strip Lucy tells Schroeder that the exact date of Beethoven's birth is not known. Schroeder then holds up a sign that says, "10 more days til Beethoven's birthday (more or less)".
In a strip from 1957, Schroeder forgets to celebrate Beethoven's birthday. The following week, he is walking around ashamed that he forgot it. He has a hard time looking at the bust on top of his piano. The boy also forgets Beethoven's birthday in strips from December 1961 and December 1967.