Calendar reform the traditional fixed arithmetic Hebrew calendar, respectively. Calendar proposals that introduce a thirteenth month or change the Julian-Gregorian system of months often also propose new names for these months. New names have also been proposed for days out of the week cycle (e.g., 365th and leap) and weeks out of the month cycle. Proposals to change the traditional month and weekday names are less frequent. The Gregorian calendar obtains its names mostly from gods of historical religions (e.g., Thursday from Nordic Thor or March from Roman Mars) or leaders of vanished empires (July and August from the first Cæsars), or
Adoption of the Gregorian calendar proved unable to keep up with the demand for copies. Catholic states such as France, the Italian principalities, Poland, Spain (along with her European and overseas possessions), Portugal and the Catholic states of the Holy Roman Empire were first to change to the Gregorian calendar. Thursday, 4 October 1582 was followed by Friday, 15 October 1582, with ten days skipped. Countries that did not change until the 18th century had by then observed an additional leap year (1700), necessitating the dropping of eleven days. Some countries did not change until the 19th or 20th century, necessitating one or two further