Twenty and 260

In the History Channel episode on Decoding the Mayan Doomsday, John Major Jenkins follows the lead of many scholars in associating the 260 day length of the tzolkin with the human gestation period. The average number for that cycle is 266 days but, as any parent knows, the number can be dramatically different. As exacting as the Maya were with their numbers, I cannot believe they would approximate something like that. But then, I have been known to be wrong. It really is just anyone’s guess.

Others have mentioned that 260 days is the time from planting to harvesting maize although another mentions it as the length of time one should rest the field before planting more maize. I have been unable to verify either of these statements.

Another supposition is the 260 days from the zenith passage of the Sun until its next zenith passage – this actually creates two periods: one of 260 days and the other of 105 days, but this is at locations near 14° North. This one is more attractive than the other theories because there are Mayan sites along that parallel.

Unfortunately, I can find nothing in the calendar that equates to the other 105 day period, nor any suggestion why the Maya would think that period was unnecessary to keep track of as well as the longer period.

Another theory has it reflected in the period of Venus as both Morning Star and Evening Star. This period is rather close to the 260 days required but not exact. Perhaps the orbit of Venus exactly fit this measurement in the past, but we cannot know for sure.

About the number twenty, Jenkins follows the usual explanation of it being the “total man”, ten fingers plus ten toes equals twenty, therefore a representation of man. His theory might be correct in this as well as in the 260 for the tzolkin.

Still, I am hesitant to jump on either bandwagon. The correspondence of the numbers to something as meaningful as pregnancy, maize cultivation, or counting on ones on digits is hard to improve on, but I still have the idea that the numbers correspond to something in the cosmos. As agriculturally intuitive as they seemed to be, there seems very little in their mathematics based on the seasons or agriculture.

Many theories abound. Venus is seen by many to be at the center of this question. Some of the better work on this can be found at John Major Jenkins’ website,, and specifically at, as well as at Keith M. Hunter’s website,

But there is nothing I can find in the cosmos to align with the twenty or the 260. Perhaps the cosmos has changed significantly since the Maya began their calendar system. It has been noted that they had occasion over the centuries to make adjustments to their calendar by a day or two to keep it in rhythm. Still, they did not seem to fiddle with the 260 day count of the tzolkin.

So where did it come from? Any ideas?

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