According to the European Union, “Europe Day held on 9 May every year celebrates peace and unity in Europe. The date marks the anniversary of the historical 'Schuman declaration' that set out his idea for a new form of political cooperation in Europe, which would make war between Europe's nations unthinkable. Schuman's proposal is considered to be the beginning of what is now the European Union.”
 

According to The World Factbook from the Central Intelligence Agency of the United States, “The evolution of what is today the European Union (EU) from a regional economic agreement among six neighboring states in 1951 to today's hybrid intergovernmental and supranational organization of 27 countries across the European continent stands as an unprecedented phenomenon in the annals of history. Dynastic unions for territorial consolidation were long the norm in Europe; on a few occasions even country-level unions were arranged - the Polish-Lithuanian Commonwealth and the Austro-Hungarian Empire were examples. But for such a large number of nation-states to cede some of their sovereignty to an overarching entity is unique.”