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
IAU Circular Astronomical Telegrams/Minor Planet Center Computer Service. Most of the announcement circulars published at Cambridge, Copenhagen, and Uccle from 1895 to the present day are available for viewing via the CBAT website. IAU Circular The International Astronomical Union Circulars (IAUCs) are notices that give information about astronomical phenomena. IAUCs are issued by the International Astronomical Union's Central Bureau for Astronomical Telegrams (CBAT) at irregular intervals for the discovery and follow-up information regarding such objects as planetary satellites, novae, supernovae, and comets. The first series of IAUCs was published at Uccle during 1920–1922 when the IAU's first CBAT was located there; the