Today is the first full moon of November, 2017. The first full moon of November has been a sort of de facto "Therianthropy Day" since the mid 1990s. It was when, 23 years ago, on the weekend of November 19 & 20, 1994, the first official AHWW howl was held.
I was unable to attend it, although I did make the two that followed. I was a broke college student and had no transportation at the time. It was fun reading the post-howl reports on the newsgroup, though.
I always felt it was a good time to have an official celebration of therianthropy, since the AHWW newsgroup itself was created in November, 1992. Very momentous for therians, November is.
It was first proposed as a sort of holiday in March of 1996, in this thread
on AHWW, should you want to investigate the history. Ultimately, AHWW decided to use it, and it stuck. It went through a few iterations of names, "International Werewolf Day", and then the less species-specific "Awereness Day" (since were is the older term for therian), and after the term therianthropy caught on, "Therianthropy Day".
So, happy "Therianthropy Day". Hope it's a good one.