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-American Day German-American Day German-American Day () is a holiday in the United States, observed annually on October 6 under . German-American Day, which celebrates German American heritage, commemorates the date in 1683 when 13 German families from Krefeld, near the Rhine, landed in Philadelphia. These families subsequently founded Germantown, Pennsylvania, the first German settlement in the original thirteen American colonies, and organized the first petition in the English colonies to abolish slavery in 1688. Originally known under the rubric of "German Day", the holiday was celebrated for the first time in Philadelphia in 1883, on the occasion of the 200th anniversary