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B.6
Just One More Calendar |
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James Colligan published in 1930 an interesting variant of a 13-month calendar. Virtually all such calendars depend upon a system of blank or missing days, or some other interruption of the seven-day weekly cycle, to accomplish a match of calendar to solar year length. |
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Colligan's calendar, however, makes no use of this stunt, showing that such interruptions are not a necessary feature of 13-month calendars, just a very common one. |
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One difficulty with reform calendars in the 20th century has been a narrow focus on the structure of a single year and a consequent neglect of the relationships between years. Neither the IFC nor the WC scheme, as you have seen, formally defines a leap year rule, although such a rule is an essential part of the calendar. A consequence of this attempt to produce a perpetual calendar is the attempt to dispose of the offending extra day in the immediate context of a single year, rather than absorbing it over several years. |
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Colligan's Pax calendar bypasses these difficulties by adding a 13 month essentially every six years. Colligan's insight is to make the added month a period of seven days, so that the weekly cycle is not disrupted by the intercalation. |
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There are some problems with this reform calendar. First, it is not very accurate with the Sun. It loses about 1.25 days per year for six years then recoups them in a single year. Second, calculation with this calendar is relatively difficult. Third, the calendar is not backward proleptic and describes only one 400-year block. Fourth, the intercalated month is intercalary, between November and December, rather than epagomenal at the end of the year, so the month indexing notation changes unnecessarily for the month of December. |
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These functions are defined and tested in the test program DTLT_184.C. |
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Some additional functions were written to further explore the Maya calendar. At the time of writing, insufficient evidence could be found in the literature to verify or disprove the correctness of the functions. These functions are published in their current state, in the hope that additional information will become available. I hope that interested readers will pursue additional information to verify or disprove these functions. |
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These functions are defined and tested in the test program DTLT_064.C. |
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