Since you don't get the joke, I will explain it to you.
Christmas is always on the 25th day of December every year. December is the 12th and last month of the year. The numerical date for Christmas is 12/25. Numerical dates look like division equations. The quotient of 12 divided by 25 equals 0.48. This decimal is equivalent to 48 percent.
Therefore, Christmas = 48%.
Do you understand now? You're welcome.