International Women's Day (IWD) is celebrated each year on March 8 and has been on this date since 1913. It was initially strongly connected to the plight of working women and the struggle for equal pay and working conditions, and with the Suffragist movement for women's voting rights. Now it is a global day to celebrate the social, economic, cultural, and political achievements of women, in addition to a call for action to accelerate gender equality. In some countries it is an observed holiday and celebrated in a similar fashion as Mother's Day in the US. Incidentally, there is also an International Men's Day, celebrated since 1999 on November 19, which promotes men's health (in accordance with the Movember Foundation in November), positive male roles, and support of gender equality.

The United Nations began to celebrate IWD in 1975, which was designated International Women's Year, and has continued to support it to this day. The UN began the adoption of an annual theme in 1996; recent themes have included “Empower Rural Women, End Poverty & Hunger” and “A Promise is a Promise—Time for Action to End Violence Against Women.” This year's theme was a hashtag, #BalanceforBetter, calling for a gender-balanced world and asking supporters to post pictures on social media of the “hands out” #BalanceforBetter pose. In addition to these visual signs of support on IWD, the group is continuing the momentum by asking supporters to enumerate ways they are working to improve gender balance in the world. While there has been a significant change both in society's attitude about and treatment of women in the past century, the goal of gender parity has not yet been reached even in developed countries, with women CEOs and leaders still being a rarity. And in some parts of the globe women still face lack of access to equal healthcare and educational opportunities, and threats of violence against them that are worse than men face in the same societies. International Women's Day will continue to bring awareness to these disparities.

Many governments, companies, and other institutions planned events or produced content to show their support of women on IWD, and there are great resources on the internationalwomensday.com website for planning and hosting an event including free downloadable content and event packs for purchase. Anyone can view and participate in the social media content related to IWD, and several physics societies also published content. The Canadian Organization of Medical Physics referenced an enlightening LinkedIn article from 2016 by Shirin Enger on The Importance of Women in Medical Physics. In 2018, the Institute of Physics (IOP) publishing gave free access to recent ebooks about women in physics, with a short Q&A with the authors. In 2019, Physics World Magazine from IOP Publishing highlighted some of the most notable content from the prior 12 months by or about women in physics. And, while not tied to IWD, the IOP also recently held a summit on gender equality in medical physics; Physics World published an excellent summary by Tami Freeman on what the summit found medical physics is getting right and where the field could improve. While medical physics is getting a lot right, there are opportunities to do better, particularly in encouraging women to seek more leadership roles, which may require more family-friendly work environments; affording women more time to participate in large group research projects; and defining a pathway to return to work in medical physics after a career break.

While International Women's Day is not specific to women in physics, it is a global opportunity to raise awareness about the achievements and importance of women in all areas of life, while also being a reminder that full equality has not yet been achieved. Hopefully medical physics will continue lead physics fields in the inclusion of women and also strive to improve where it can.

Poster for International Women's Day demonstrating the “hands out” #BalanceforBetter pose (internationalwomensday.com)