Day_of_the_founding_of_the_German_Empire
The Day of the founding of the German Empire (German: Reichsgründungstag) was an annual celebration on the anniversary of the proclamation of the German Empire on 18 January 1871 in the Palace of Versailles.
The North German Confederation had already officially adopted the name "German Reich" in its Constitution by 1 January 1871, so constitutionally speaking, 18 January was not the day of the founding.