Example image of eyePlorer eyePlorer map for '2003 in the European Union': 2003 European Union European Liberal Democrat and Reform Party Greece High Representative for the Common Foreign and Security Policy Italy January 1 Javier Solana Party of European Socialists Pat Cox Presidency of the Council of the European Union President of the European Commission President of the European Parliament Romano Prodi February 1 Treaty of Nice Malta March 8 March 23 Slovenia April 9 April 12 Hungary April 16 Athens Treaty of Accession 2003 Lithuania May 11 May 17 Slovakia June 8 Poland Czech Republic June 14 July 1 Eurozone September 14 Sweden Estonia October 4 Treaty establishing a Constitution for Europe Timeline of European Union history