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See the SCDTL text on the CD for the discussion of the code. |
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9.7.3
Alexandrian Style Calendars |
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Several calendars are called ''Alexandrian style", because they are structurally related. Such calendars divide the year into 12 equal months of 30 days, adding an epagomenal period of five or six days at the end of the year. Leap years occur every fourth year. The placement of the leap year varies, but most frequently it is considered to be the third year of every four. The leap year causes the epagomenal period to be increased from five days to six. |
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The essential differences among calendars of this type are the epoch and the position of the leap year. |
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9.7.3.1
Alexandrian Calendar |
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The Alexandrian calendar is, historically, the first of the Alexandrian style calendars. |
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This section discusses the structure of the Alexandrian calendar and introduces historical material as background. |
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9.7.3.1.1.1
Structural Details |
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The Alexandrian calendar arranges the year as 12 equal months of 30 days, followed by an epagomenal period of five days, or six days in leap years. The leap year is observed every fourth year, beginning with the third. |
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The largest repetitive unit in the Alexandrian calendar is the quad of four years, which is 365 + 365 + 366 + 365 = 1,461 days. The term quad is used within SCDTL to denote this unit, which is common to many calendars and is not original with the calendar itself. A consequence of this unit is that the Alexandrian calendar considers the length of the year to be 1,461 days/4 years = 365.25 days per year. This estimate of the length of the tropical year is too long and therefore causes the months of the Alexandrian calendar to rotate slowly out of synchronization with the seasons. |
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The calendar was used in several different areas under different circumstances, so there is some variation in actual usage. The calendar itself did not recognize the week as a unit. |
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