Question: When did East Germany and the country that hosted the 1965–66 season of the Bundesliga football league unite?

full_context: Document 1: Unification of Germany: The unification of Germany into a politically and administratively integrated nation state officially occurred on 18 January 1871, in the Hall of Mirrors at the Palace of Versailles in France. Princes of the German states, excluding Austria, gathered there to proclaim Wilhelm I of Prussia as German Emperor after the French capitulation in the Franco - Prussian War. Unofficially, the de facto transition of most of the German - speaking populations into a federated organization of states had been developing for some time through alliances formal and informal between princely rulers -- but in fits and starts; self - interests of the various parties hampered the process over nearly a century of autocratic experimentation, beginning in the era of the Napoleonic Wars, which saw the dissolution of the Holy Roman Empire of the German Nation (1806), and the subsequent rise of German nationalism.
Document 2: Hanover: Hannover 96 (nickname Die Roten or 'The Reds') is the top local football team that plays in the Bundesliga top division. Home games are played at the HDI-Arena, which hosted matches in the 1974 and 2006 World Cups and the Euro 1988. Their reserve team Hannover 96 II plays in the fourth league. Their home games were played in the traditional Eilenriedestadium till they moved to the HDI Arena due to DFL directives. Arminia Hannover is another very traditional soccer team in Hanover that has played in the first league for years and plays now in the Niedersachsen-West Liga (Lower Saxony League West). Home matches are played in the Rudolf-Kalweit-Stadium.
Document 3: 1969–70 Bundesliga: The 1969–70 Bundesliga was the seventh season of the Bundesliga, West Germany's premier football league. It began on 16 August 1969 and ended on 7 June 1970. Bayern Munich were the defending champions.
Document 4: 1963–64 Bundesliga: The 1963–64 Bundesliga season was the inaugural season for a single division highest tier of football in West Germany. It began on 24 August 1963 and ended on 9 May 1964. The first goal was scored by Friedhelm Konietzka for Borussia Dortmund in their game against Werder Bremen. The championship was won by 1. FC Köln. The first teams to be relegated were Preußen Münster and 1. FC Saarbrücken.
Document 5: German reunification: The German reunification (German: Deutsche Wiedervereinigung) was the process in 1990 in which the German Democratic Republic (GDR / DDR / East Germany) joined the Federal Republic of Germany (FRG / West Germany) to form the reunited nation of Germany, and when Berlin reunited into a single city, as provided by its then Grundgesetz constitution Article 23. The end of the unification process is officially referred to as German unity (German: Deutsche Einheit), celebrated on 3 October (German Unity Day) (German: Tag der deutschen Einheit). Following German reunification, Berlin was once again designated as the capital of united Germany.
Document 6: Germany: After Germany surrendered, the Allies partitioned Berlin and Germany's remaining territory into four military occupation zones. The western sectors, controlled by France, the United Kingdom, and the United States, were merged on 23 May 1949 to form the Federal Republic of Germany (Bundesrepublik Deutschland); on 7 October 1949, the Soviet Zone became the German Democratic Republic (Deutsche Demokratische Republik). They were informally known as West Germany and East Germany. East Germany selected East Berlin as its capital, while West Germany chose Bonn as a provisional capital, to emphasize its stance that the two - state solution was an artificial and temporary status quo.
Document 7: Territorial evolution of Germany: The territorial changes of Germany include all changes in the borders and territory of Germany from its formation in 1871 to the present. Modern Germany was formed in 1871 when Otto von Bismarck unified most of the German states, with the notable exception of Austria, into the German Empire. After the First World War, Germany lost about 10% of its territory to its neighbours and the Weimar Republic was formed. This republic included territories to the east of today's German borders.
Document 8: 1980–81 Bundesliga: The 1980–81 Bundesliga was the 18th season of the Bundesliga, West Germany's premier football league. It began on 15 August 1980 and ended on 13 June 1981. Bayern Munich were the defending champions.
Document 9: History of Germany (1945–1990): The intended governing body of Germany was called the Allied Control Council. The commanders - in - chief exercised supreme authority in their respective zones and acted in concert on questions affecting the whole country. Berlin, which lay in the Soviet (eastern) sector, was also divided into four sectors with the Western sectors later becoming West Berlin and the Soviet sector becoming East Berlin, capital of East Germany.
Document 10: States of Germany: After the Nazi Party seized power in January 1933, the Länder increasingly lost importance. They became administrative regions of a centralised country. Three changes are of particular note: on January 1, 1934, Mecklenburg-Schwerin was united with the neighbouring Mecklenburg-Strelitz; and, by the Greater Hamburg Act (Groß-Hamburg-Gesetz), from April 1, 1937, the area of the city-state was extended, while Lübeck lost its independence and became part of the Prussian province of Schleswig-Holstein.
Document 11: 1986–87 Bundesliga: The 1986–87 Bundesliga was the 24th season of the Bundesliga, the premier football league in West Germany. It began on 8 August 1986 and ended on 17 June 1987. FC Bayern Munich were the defending champions.
Document 12: Berlin Wall: In 1989 a series of revolutions in nearby Eastern Bloc countries -- Poland and Hungary in particular -- caused a chain reaction in East Germany that ultimately resulted in the demise of the Wall. After several weeks of civil unrest, the East German government announced on 9 November 1989 that all GDR citizens could visit West Germany and West Berlin. Crowds of East Germans crossed and climbed onto the Wall, joined by West Germans on the other side in a celebratory atmosphere. Over the next few weeks, euphoric people and souvenir hunters chipped away parts of the Wall; the governments later used industrial equipment to remove most of what was left. The ``fall of the Berlin Wall ''paved the way for German reunification, which formally took place on 3 October 1990.
Document 13: 1965–66 Bundesliga: The 1965–66 Bundesliga was the third season of the Bundesliga, West Germany's premier football league. It began on 14 August 1965 and ended on 28 May 1966. Werder Bremen were the defending champions.
Document 14: Dresden: Since German reunification in 1990 Dresden is again a cultural, educational and political centre of Germany and Europe. The Dresden University of Technology is one of the 10 largest universities in Germany and part of the German Universities Excellence Initiative. The economy of Dresden and its agglomeration is one of the most dynamic in Germany and ranks first in Saxony.  It is dominated by high-tech branches, often called “Silicon Saxony”. The city is also one of the most visited in Germany with 4.3 million overnight stays per year. The royal buildings are among the most impressive buildings in Europe. Main sights are also the nearby National Park of Saxon Switzerland, the Ore Mountains and the countryside around Elbe Valley and Moritzburg Castle. The most prominent building in the city of Dresden is the Frauenkirche. Built in the 18th century, the church was destroyed during World War II. The remaining ruins were left for 50 years as a war memorial, before being rebuilt between 1994 and 2005.
Document 15: 2011–12 Bundesliga: The 2011–12 Bundesliga was the 49th season of the Bundesliga, Germany's premier football league. The season started on 5 August 2011 with the opening match involving defending champions Borussia Dortmund and ended with the last games on 5 May 2012. The traditional winter break was held between the weekends around 17 December 2011 and 20 January 2012.
ground_truth: 1990
sub_queries: 1965–66 Fußball-Bundesliga >> country Answer: West Germany
when did east germany and West Germany unite Answer: 1990