Perpetual calendar

Perpetual calendar

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Langematik-Perpetual
mit ewigem Kalender

A perpetual calendar keeps track of the date, the day of the week, the month, the year, including leap years, and sometimes even the century. Because of the complex rules of the Gregorian calendar, which include varying lengths of months and leap years every four years, a perpetual calendar is an extraordinary exercise in the design and manufacture of this complication.