Determination of the day of the week row C) to find the dominical letter that is E. The letter for September 18 is B, so the day of the week is Thursday. Use 16 (in the Julian century row, column E) and 76 (in row D) to find the dominical letter that is A. February 23 is a "D" day, so the day of the week is Wednesday. In a handwritten note in a collection of astronomical tables, Carl Friedrich Gauss described a method for calculating the day of the week for 1 January in any given year. He never published it. It was finally included in
Determination of the day of the week possible to do all the calculations in one's head with a little practice). None of the methods given here perform range checks, so unreasonable dates will produce erroneous results. Every seventh day in a month has the same name as the previous: "Corresponding months" are those months within the calendar year that start on the same day of the week. For example, September and December correspond, because September 1 falls on the same day as December 1. Months can only correspond if the number of days between their first days is divisible by 7, or in other words, if their