This calendar runs from January 1 of the year 1600 to December 31 of the year 2799. It is based on the repetitive cycle of 400 years and the solar cycle that is 28 years. It works by the "Sunday letter." Only the perpetual calendars fulfill the basic condition of allowing the deduction of any of your essential data from the others (the numbers of the year, month, week and day). But almost all the known perpetual analog calendars have little perpetual, their calculations are limited to about 50 years.