The flag of unity at midnight on 3 October 1990 in front of the Reichstag building. Bundesarchiv, Bild 183-1990-1003-400 / Grimm, Peer / CC-BY-SA [CC-BY-SA-3.0-de (http://creativecommons.org/licenses/by-sa/3.0/de/deed.en)]. German Federal Archives. Available from Wikimedia Commons.
October 3 is German Unity Day (Tag der Deutschen Einheit). It is the anniversary of German reunification, and has been a national holiday in Germany since 1990, when reunification took place. Between 1954 and 1990, June 17 had been "Day of German Unity." The day had commemorated the Uprising of 1953 in East Germany.
A celebration is held every year in the capital of the German state that currently presides over the Bundesrat, the legislative body that represents the sixteen German states. Speeches are given by officials. The speech given at last year's celebration in Stuttgart by President Joachim Gauck is available online. After the ceremony, there is a citizens' festival (Bürgerfest), which includes cultural exhibits, music, and dance.
This year's celebration is in Hannover, the capital of Lower Saxony (Niedersachsen). The 108-page program is available for download.
A street festival is also held at the Brandenburg Gate in Berlin. It includes beer gardens, food, music, amusement rides, games and theater performances.
Day of German Unity
Dennis, Matthew, ed. Germany: Holidays and Celebrations. World Geography and Culture Online. Facts On File, Inc.
German Unification Day - Street Party
German Unity Day
Speech to Mark the Day of German Unity
Tag der Deutschen Einheit