Determination of the day of the week not a Gregorian leap year, (but 19 in the Julian column indicates that it "is" a Julian leap year, as are all Julian "x"00 years). 20 indicates that 2000 is a leap year. Use Jan and Feb only in leap years. For determination of the day of the week (1 January 2000, Saturday) For determination of the dominical letter (2000, BA) For determination of the doomsday (2000, Tuesday) Note that the date (and hence the day of the week) in the Revised Julian and Gregorian calendars is the same from 14 October 1923 to 28 February AD 2800 inclusive and
Eight-day week a day. Further, they also counted the ending night period, giving rise to periods of time with more nights than days. In Irish, the term "nómad" is used to signify a small number of days and is exactly the length of the nine night week as in "co cend nomaide" - a period of time with nine nights bracketing eight days. The nine nights divided nicely into a sidereal month of 27 nights. In Welsh a similar word "wythnos" meaning "a week" literally means "an eight-night" since it started and ended with a period of night bracketing seven days. Similarly