What's with the random holidays popping up?

I like the random days so far. I had TV Premiere Day which was easy enough to accomplish, and just now I've had Rebate Day, which was also easy. Neither of them have broken immersion for me. My only issue so far is that I wish there was even more customisation available for the holidays you can create yourself.

The Brawling Day just appeared in my calendar but as I'm not playing Criminals in this save, I have no use for it, and it got deleted.