Finland
February 6, Sámi National Day
February 6, the date when the first Sámi congress was held in 1917 in Trondheim, Norway.
April 9, Finnish Language Day / Mikael Agricola Day
Mikael Agricola is considered the father of the Finnish literary language.
November 6, The Finnish Swedish Heritage Day / Svenska dagen
The day celebrates the Swedish-speaking population of Finland, their culture, and the bilingualism of Finland.
November 27, The Karelian Language Day
On this day in 2009, Karelian was granted minority language status in Finland, and thus Karelian became one of the minority languages of the European Union.
I also created a shared Google Drive spreadsheet if you want to add your language days to it:
https://docs.google.com/spreadsheets/d/14EJ8wBVaHB7RPrMFNJDRZaXp37mIRt72QvwXRmAsjrE/edit?usp=sharing
