"For breakfast this morning, my youngest daughter Josephine spotted a headline saying it was International Women's Day," Mary wrote (roughly translated from Danish).
"She asked, 'What kind of day is this?'," Mary continued.
"I thought briefly about my answer and said that for her it is a day where she must believe and trust that she can come into being and do everything she dreams of without anyone or anything stopping her... because she's a girl."
The Crown Princess added: "She did not ask any further questions, so maybe my answer was no surprise to her. Maybe it's something she takes for granted. But that's not the case for many other girls around the world."
The Princess continued her post: "International Women's Day has different meanings depending on where in the world you live. But no matter where you live, it is an important day where we not only talk about how far we have come, but also about where we have come from and where we want to go."
She explained she had attended three separate meetings that day, including a round table discussion with UN Women about diversity and inclusion in leadership.
The Princess ended the caption: "For me, equality is not about everyone being equal, but - as I said to Josephine - [it is] about gender not having a role to play when opportunities present themselves and decisions are made... or when following one's dreams."
Later in the day, the Danish Palace shared another image to Instagram of Mary after filming a video with a special message for the poignant date.
The Princess filmed the clip during an online event in Denmark featuring speeches, performances and guest appearances in celebration of International Women's Day.
As the day is marked by strong female leaders, perhaps we take a lesson from this in itself - these leading women all started from scratch somewhere.
It's never too late to be advocates for change, particularly within gender discourse.
Happy International Women's Day, indeed.
This article originally featured on our sister site, Now To Love.