Sedantag (Sedan Day) was a semi-official holiday that was observed on September 2 in the German Empire. It commemorated the victory of King Wilhelm of Prussia in the Battle of Sedan, which was fought on 1 September 1870 during the Franco-Prussian War.
Celebration festivities varied, and could include parades, patriotic speeches, musical performances, and pageants. In schools, celebrations were held in classrooms or auditoriums. Not all parts of the German Empire observed Sedantag.
Sedantag was also celebrated by German-Americans.
San Francisco Call, 2 September 1895, page 2
On 27 August 1919, the Innenministerium of the Weimar Republic declared that Sedantag celebrations would no longer be held.
Kieler Erinnerungstag 2. September: Der Sedantag
Memories of Sedan Day Festivities in the 1870s (Retrospective Account, 1930)
Zimmer, Oliver. Remaking the Rhythms of Life: German Communities in the Age of the Nation-State. Oxford, England: Oxford University Press, 2013.