The UNESCO Executive Board decided in October 2018 to endorse a recommendation, coordinated by the International Mathematical Union, to proclaim an International Day of Mathematics on 14th March each year. This recommendation is on the agenda for the UNESCO General Conference in November 2019 an, if adopted, will have its first official celebration on 14th March 2020, where the proposed theme is ‘Mathematics is Everywhere‘.
Preparations in anticipation for the adoption seem to be heating up, with a publicity drive underway. The IDM website says it will share free materials, projects, ideas and software, as well as a map of worldwide events and gatherings, all in multiple languages and under open licenses. You can sign up for a “one or two emails per month at most” mailing list to keep informed.
More information: The IMU wants to make π Day the International Day of Mathematics (October 2018).