Sabbath a synonym of midnight-to-midnight "Saturday" (literally, Saturn's day in at least a dozen languages): this is a simplification of the use of "Sabbath" in other religious contexts, where the two do not coincide. (Using midnight instead of sundown as delimiter dates back to the Roman Empire.) In over thirty other languages, the common name for this day in the seven-day week is a cognate of "Sabbath". "Sabbatini", originally "Sabbadini", often "Sabatini", etc., is a very frequent Italian name form ("Sabbatos" is the Greek form), indicating a family whose ancestor was born on Saturday, Italian "sabato"; "Domenico" indicated birth on Sunday.
Determination of the day of the week since the start of the century, and then add these together along with the number of years since the start of the century, and the day number of the month. Eventually, one ends up with a day-count to which one applies modulo 7 to determine the day of the week of the date. Some methods do all the additions first and then cast out sevens, whereas others cast them out at each step, as in Lewis Carroll's method. Either way is quite viable: the former is easier for calculators and computer programs; the latter for mental calculation (it is quite