The San Francisco Conference on 26 June 1945, at which the United Nations Charter was signed. © UN Photo/Rommel

UN Day celebrates the anniversary of the day the UN Charter entered into force in 1945.

This founding treaty was initially signed in San Francisco, on 26 June 1945. After it was ratified, it entered into force on 24 October, marking the birth of the United Nations.

The Preamble of the Charter lays out the UN's core aims:

"We the peoples of the United Nations determined to save succeeding generations from the scourge of war... to reaffirm faith in fundamental human rights, in the dignity and worth of the human person, in the equal rights of men and women and of nations large and small... and to promote social progress and better standards of life in larger freedom... do hereby establish an international organization to be known as the United Nations."

The 24th of October has been celebrated as United Nations Day since 1948. This year's UN Day marks the 73rd anniversary of the UN.

The United Nations Charter on the date of its signing. © UN Photo/Rosenberg