It's King Friday's birthday!!
Mr Rogers made King Friday XIII's birthday on every Friday the 13th, which I think is super cool if you're a kid and your birthday falls on a day that many people are bothered by.
I've always liked the number 13 (3 is good, 1 is good, prime; it keeps popping up in my life on cars, addresses, etc. My first somewhat serious job was on the 13th floor of a building numbered 1301. My boss told me the rent was super cheap, which I believe, since so was he)
Plus, IT'S A FRIDAY and I don't see how anything can be wrong with that....