International Mother Language Day

On the way to trying to figure out if "mother tongue/language" in Italian was "madrelingua" or "lingua madre," I found a post at the Scioglilingua forum/blog (which hasn't been updated for a while probably because linguist Giorgio De Rienza passed away) that said "Lo scorso 21 febbraio è stata celebrata in tutto il mondo la giornata internazionale della madrelingua." [Last February 21 international mother language day was celebrated throughout the world.]

I had no idea such a day existed. The United Nations is the source of the day, and Wikipedia offers a thorough explanation: 

The date corresponds to the day in 1952 when students from the University of Dhaka, Jagannath College and Dhaka Medical College, demonstrating for the recognition of Bengali as one of the two national languages of East Pakistan, were brutally shot dead by police (then under Pakistan government) near the Dhaka High Court in the capital of present-day Bangladesh. 

Luckily, the Corriere della Sera newspaper hasn't deleted the blog/forum (I see it as a blog, but they categorize it as "forum"), so I'm going to go back to attempt to translate the post that explains the difference between those two words.