Determination of the day of the week ISO 8601. The day designated with 7 may also be counted as "0", by applying the arithmetic modulo 7, which calculates the remainder of a number after division by 7. Thus, the number 7 is treated as 0, 8 as 1, 9 as 2, 18 as 4 and so on. If Sunday is counted as day 1, then 7 days later (i.e. day 8) is also a Sunday, and day 18 is the same as day 4, which is a Wednesday since this falls three days after Sunday. The basic approach of nearly all of the methods to calculate the
German Unity Day choice to commemorate the reunification could have been the day the Berlin Wall came down: 9 November 1989, which coincided with the anniversary of the proclamation of the German Republic in 1918, and the defeat of Hitler's first coup in 1923. However, 9 November was also the anniversary of the first large-scale Nazi-led pogroms against Jews in 1938 ("Kristallnacht"), so the day was considered inappropriate as a national holiday. (See November 9 in German history.) Therefore, 3 October 1990, the day of the formal reunification, was chosen instead and replaced the "Day of German Unity" on 17 June, the national