The Charter entered into force on 24 October 1945, following ratification by the five permanent members of the United Nations Security Council—China, France, the Soviet Union, the United Kingdom, and the United States—and a majority of the other signatories; this is considered the official starting date of the United Nations, with the first session of the General Assembly, representing all 51 initial members, opening in London the following January. The General Assembly formally recognized 24 October as United Nations Day in 1947, and declared it an official international holiday in 1971. With 193 parties, most countries have now ratified the Charter.