United Nations Day, on 24 October, marks the anniversary of the entry into force in 1945 of the UN Charter. With the ratification of this founding document by the majority of its signatories, including the five permanent members of the Security Council, the United Nations officially came into being.
There is no other global organization with the legitimacy, convening power and normative impact of the United Nations. No other global organization gives hope to so many people for a better world and can deliver the future we want. Today, the urgency for all countries to come together, to fulfil the promise of the nations united, has rarely been greater.
UN Day, celebrated every year, offers the opportunity to amplify our common agenda and reaffirm the purposes and principles of the UN Charter that have guided us for the past 77 years.
International days and weeks are occasions to educate the public on issues of concern, to mobilize political will and resources to address global problems and to celebrate and reinforce the achievements of humanity. The existence of international days predates the establishment of the United Nations, but the UN has embraced them as a powerful advocacy tool.
source: un.org