It is taken as a fact in many books and specialized publications that the Maya calendrical system - the Haab' and the Tzolk'in - was more accurate and closer to the real solar year than the Gregorian calendar (even though reputable sources claim it is 365 days compared to 365.2425 days). But how is this really so? In all the studies I've read there is just a description of the calendars but not how that accuracy is obtained. How's that?

Update (05/04/2018): I've found multiple resources that support the premise on which this question is asked. However, I do recognize the issue of finding a relevant primary source (such as a Maya stela or a given codex). There was a discussion on Wikipedia regarding Maya expert Coe disproving this premise, however, since this question was asked, the author of this other question has edited it saying that Mr. Coe includes no references that support his statement in a section the user found. The question remains open since I'd like to compile more sources from other users.

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    Where do you get 365.21 from? Wikipedia suggests 365 for the Haab (and 260 for the Tzolk'in). Similarly where do you get 365.25 from (the Gregorian calendar actually uses 365.2425)? – Henry Mar 24 '18 at 1:57
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    Apparently the idea that the Mayan calendar is more accurate is a myth – Gort the Robot Mar 24 '18 at 2:30
  • @Henry, those numbers come from a small book I bought but it is clear that those are somewhat arbitrary so I'm editing the question. Steven, interesting reading, but I see the general structure of the article with poor references, I will keep looking for additional sources. – Pablo Ivan Mar 24 '18 at 2:55
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    To measure a calendar's accuracy you look into whether it's good at predicting events like solstices, equinoxes, lunar cycles, eclipses, etc. – Denis de Bernardy Mar 24 '18 at 7:04
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    It is a myth. See a discussion here: hsm.stackexchange.com/questions/5790/… – Alex Mar 24 '18 at 13:05

The Gregorian, and indeed the Roman, Egyptian, and Chinese calendars all include occasional intercalary periods to make up the 0.24 of a solar day that is left over when using a 365-day calendar. These systems count solar years more accurately than the Mayan calendar.

The Tzolk'in at 260 days seems unrelated to the solar year; the Haab''s length of 365 days does seem related. However, in neither case were intercalary periods added. Doing so could complicate calculations with the Calendar Round. Maintaining continuity was a reason to stick with the inaccurate Haab'. According to David Bolles, in "The Mayan Calendar, The Solar - Agricultural Year, and Correlation Questions":

It is generally accepted by Mayanists today that the Mayan calendar was a “floating” calendar, in which no attention was given to keeping the calendar in sync with the solar - agricultural year. As Michael Coe in his book The Maya puts it, the Maya had “a ‘Vague Year’ of 365 days, so called because the actual length of the solar year is about a quarter-day more, a circumstance that leads us to intercalate one day every four years to keep our calendar in march with the sun, but which was ignored by the Maya.” Earlier Thompson wrote that “The Maya made no attempt to intercalate days in the count of the years to bring the year of 365 days into conformity with the solar year. Such a correction would have played havoc with the whole orderly plan of the calendar and would have disorganized the elaborate system of lowest multiples of different time cycles, which were of the highest importance for divinatory and ritualistic purposes.”

That said, the Maya calendar does seem more precise than the Gregorian one. Finding the number of days that elapsed between two dates is easier without leap days.

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  • The thing that baffles me is that, as far as I've checked, neither Thompson nor Coe provide primary references that support their statements. – Pablo Ivan Apr 7 '18 at 5:42
  • There's also a small subtlety in your citation, since the author writes "Mayan calendar" instead of the correct form "Maya calendar", thus becoming somewhat unreliable as a source given the ongoing debate of intercalary days among the Maya. – Pablo Ivan Apr 7 '18 at 6:04
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    @PabloIvan Those authors made the claim; they couldn't cite something's absence. Do you have a specific reason to doubt their conclusion? – Aaron Brick Apr 7 '18 at 6:17
  • Great answer! I really don't have a reason, what you said reminds me of an archaeology principle "there's no negative evidence". I just wanted to be sure all claims are supported by either strong evidence or authorities in the field. Thanks for your answer. – Pablo Ivan Apr 7 '18 at 6:23
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    You are welcome. By the way, "Mayan" is or was a pretty common adjectival form in English, so I don't think its use reflects badly on an author. – Aaron Brick Apr 8 '18 at 3:16

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