May 12 was chosen for the Celebration of Women in Mathematics because it is the birthdate of Maryam Mirzakhani. The initiative was  proposed by the Women's Committee of the Iranian Mathematical Society and voted by a vast majority of attendees to (WM)², the World Meeting for Women on Mathematics on last July 31 in Rio.

Several suggestions for local activities around May 12 are listed here.Please feel free to organize one and mention it on May 12 website.

The initiative is  supported by several organisations for women in mathematics worldwide (European Women in Mathematics, Association for Women in Mathematics, African Women in Mathematics Association, Indian Women and Mathematics, Colectivo de Mujeres Matemáticas de Chile andthe Women's Committee of the Iranian Mathematical Society).

The initiative is welcoming  the support of more organizations, the conditions are as follows

- accepting to put the name of their organization on the website
- sending a contact name
- disseminating the initiative through their channels
- post the information of their activities around May 12 on the May 12 website.

Organizations are invited to contact the coordination group of May 12  through the website.

More information here.