The International Day of Peace, sometimes unofficially known as World Peace Day, is a holiday observed annually on 21 September. It is dedicated to world peace, and specifically the absence of war and violence, such as might be occasioned by a temporary ceasefire in a combat zone for humanitarian aid access. The day was first celebrated in 1982, and is kept by many nations, political groups, military groups, and people. In 2013 the day was dedicated by the Secretary-General of the United Nations to peace education, the key preventive means to reduce war sustainably.