International Day of Peace (September 21)

In 1981, the United Nations General Assembly declared that the opening day of the General Assembly in September will be officially devoted to commemorating and strengthening the ideals of peace both within and among all nations and peoples (A/RES/36/67).
Then in 2001, UN GA Resolution 55/282 established that September 21 would become an annual International Day of Peace.

The UN is calling for member states, UN organs, regional agencies and NGOs to celebrate this day, and to cooperate with the UN to realize ceasefire and non-violence on a global scale.