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 G. Leap years have two Sunday Letters, so for January and February calculate the day of the week for 1 January and for March to December calculate the day of the week for 1 October. Leap years are all years which divide exactly by four with the following exceptions: In the Gregorian calendar – all years which divide exactly by 100 (other than those which divide exactly by 400). In the Revised Julian calendar – all years which divide exactly by 100 (other than those which give remainder 200 or 600 when divided by 900). Use this table for finding