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
Leap week calendar full weeks (364 or 371 days). Leap week calendars vary on whether the concept of month is preserved and whether the month (if preserved) has a whole number of weeks. The Pax Calendar and Hanke-Henry Permanent Calendar (formerly the Common-Civil-Calendar-and-Time) preserve or modify the Gregorian month structure. The ISO week date and the Weekdate Dating System are examples of leap week calendars that eliminate the month. Most leap week calendars take advantage of the 400-year cycle of the Gregorian calendar, which has exactly 20,871 weeks. With 329 common years of 52 weeks plus 71 leap years of 53 weeks, leap