@lea_eule@queer.party probably, I never realise before I read it on that day :) There's another possible #internationalnonbinaryday on march 15: https://villiljos.tumblr.com/post/155628645164/international-genderqueernon-binary-day

And trans day of grandiosity on june 6, of course. (less specific, but the only one i have ever celebrated.)