World Teachers' Day (5 October)

Nothing to do with World Teachers as imagined in Theosophy....
https://en.wikipedia.org/wiki/Maitreya_(Theosophy)
Rather, established by UNESCO (1994) to commemorate the adoption of a document entitled _Recommendation Concerning the Status of Teachers_ by UNESCO with the International Labour Organization (Paris, 5/10/1966).
https://www.unesco.org/en/days/teacher
If you're enjoying all these International Days and want more, there's a link from that page to an extensive list of UNESCO International Days, most of which have nothing to do with language.