The International Day of Mathematics (IDM) is a worldwide celebration.March 14 was chosen as the date for the IDM because it was already celebrated in many countries as Pi Day, based on the fact that some countries write it as 3/14 and the mathematical constant Pi is approximately 3.14.

The International Day of Mathematics project is led by the International Mathematical Union with the support of numerous international and regional organizations from all over the world. It was proclamated by UNESCO on the 40^th session of the General Conference, November 26, 2019. The first celebration was held on March 14, 2020. The theme chosen for the first IDM was Mathematics is Everywhere.

Source from: https://www.idm314.org/