December 15th is Esperanto Day! Esperanto is a created language, started in the 1880s by L. L. Zamenhof. December 15th was his birthday, and it’s suitably close to the winter holidays that it’s become the largest Esperanto holiday.
I’ve been studying Esperanto every day for a bit more than 500 days, and I’m still having a lot of fun with it.
I wrote more about Esperanto Day last year.