Ropp's Perpetual Calendar, Updated
"Good for Three Centuries" Original in the Home Comfort Cook Book, 1892
To learn to use the calendar, let's use an example. Say your birthday is on May 18, and you want to know on what day of the week it will fall ten years hence, in 2011.
The perpetual calendar above deals only with the Gregorian system. There are many other kinds, including Aztec, Babylonian, Chinese, Egyptian, French republican, Greek, Hindu, Jewish, Julian, Mayan, Muslim, Roman republican, and Tibetan. Only two of these are of interest to most Orthodox Christian citizens of this country, the Gregorian and the Julian. As Americans they have to follow the Gregorian in their secular life, but as Orthodox Christians they should follow the Church calendar, which is most similar to the old Julian system. Let's examine the accuracy issue between the Julian and the Gregorian.
The year 2000, for instance, was evenly divisible by 100 and by 400, and was therefore a leap year in both the Gregorian and the Julian. So will 2400, 2800, 3200, etc., be leap years in both systems. But the years 1700, 1800, and 1900 were not Gregorian leap years. Neither will 2100, 2200, 2300, 2500, 2600, 2700, etc., be leap years. Although they are evenly divisible by 100, they are not evenly divisible by 400. That makes them 365-day ("non-leap") years. This rule eliminates 3 leap years every 400 years, thereby achieving greater accuracy and increasing the discrepancy between the calendars by 3 days per four centuries, or an average of 0.75 days per century. The Church calendar is quite similar to the Julian calendar. The Julian, introduced in Rome in 56 B.C., is 365 days and 6 hours long. It was used in England into the eighteenth century and in Russia into the twentieth century. The difference between the Church calendar and the Gregorian is that the Church calendar never simply eliminated ten days, as was done by the Gregorian when it was first introduced, and does not make the additional correction of requiring centesimal years (those evenly divisible by 100) to be evenly divisible also by 400 to qualify as leap years. Therefore it has more leap years than the Gregorian, and this accounts for its greater average year length.
How soon will the difference between the two calendars be 14 days? Well, we have to look for the next year that the Church calendar recognizes as a leap year but the Gregorian does not, i.e. in a year evenly divisible by 100 but not by 400. That has to be the year 2100. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||

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