August 13th Gregorian. It was August 13 1521 - 62 years prior to Gregorian reform reaching Mexico. The problem is that Aug 13 Jul correlated with the indigenous dates 1-Coatl and 20-Miccailhuitontli produces a Mexican calendar which basically doesn't work as it shifts equinox dates out by 10 days (and yes, I know what the figure of 10 days looks like) amongst other problems. Replace Aug 13 Jul with Aug 3 Jul and 1-Coatl / 20-Miccailhuitontli work perfectly. So basically someone somewhere appears to have lied about a date. I appreciate the offer but I've been up to my armpits in this stuff for the last month and am painfully well acquainted with the mechanics of Gregorian calendar reform.
The essence of the problem is that it basically looks as though someone recorded a Gregorian date, 62 years prior to reform, which obviously didn't happen, which is why I was wondering whether anyone knew of a precedent for a Catholic culture getting a date wrong. In other words I'm just weighing up the probabilities because this seems to be one instance where if the indigenous date was falsified it would have shown up in the form of an inconsistency within the Mexican calendar as a whole (it being mathematically very complex).
The problem is also that it's difficult communicating exactly what's wrong in succinct form. I've written at length on this. I can post my long droning essay here if it'll help.
The Tonalpohualli in Solar Time
Being the shorter of the two cycles, the Tonalpohualli count repeats with greater frequency within the Xiuhpohualli year. The first day of each new Tonalpohualli count will therefore necessarily occur on a different day of each consecutive Xiuhpohualli year, and often one Xiuhpohualli year may contain the tail end of one Tonalpohualli, then the next cycle in its entirety, then terminate just after the beginning of a third cycle. One analogy made earlier in this narrative likened the interaction of teteton and day-signs to a pair of cogged wheels with varying numbers of teeth. Returning to this analogy, the Tonalpohualli and Xiuhpohualli might be imagined as two much larger wheels, one with 260 teeth, the other with 365. These larger wheels must turn many times before resuming their original alignment which, in terms of the calendar as a whole, amounts to fifty-two years; that is, it takes fifty-two years for the Tonalpohualli count to reoccupy the same group of 260 solar days upon which it began fifty-two years earlier. This large cycle amounts to the fifty-two years defined as one Xiuhmolpilli.
The year is named after the Tonalpohualli configuration of teteton and day-sign which falls upon the year-bearer day of the Xiuhpohualli calendar. Owing to the mathematical framework involved, all thirteen numerals, but only four of the twenty day-signs can occupy this day (these being the series III group referred to earlier: Acatl, Tecpatl, Calli, and Tochtli) so as each year draws to its end, each year-bearer day forges a different combination of teteton and day-sign resulting in a progressive sequence of named years: Ome Acatl (Two Reed), Yei Tecpatl (Three Knife), Nahui Calli (Four House), Macuilli Tochtli (Five Rabbit), Chicoce Acatl (Six Reed), Chicome Tecpatl (Seven Knife) and so on. After fifty-two years, the calendar will have cycled through all possible configurations of four day-signs and thirteen teteton, following which the sequence returns to its beginning at the start of a new Xiuhmolpilli. Whilst this may seem a complex system, the mathematics are surprisingly simple. The calculations regarding which Tonalpohualli day constitutes each new year-bearer are only a variation on those by which the first day of 2006 was a Sunday, that of 2007 was a Monday, and that of 2008 will be a Tuesday.
Many attempts have been made to correlate the Tonalpohualli count with the Xiuhpohualli calendar and with frequently questionable results, and it seems that most of these problems may arise from a single inaccurate date. A great number of accounts attribute Cuautemoc's surrender to Hernan Cortés to the 13th of August, 1521, a date equivalent to Ce Coatl in the Tonalpohualli count and F1.7.20 in the Xiuhpohualli - the last day of Miccailhuitontli. The great problem with this is that F1.7.20 and the 13th August, 1521 only work together if the TTTM correlation is out by a whole ten days, which patently it is not. Suggestions that indigenous records are in error and that 13th August, 1521 is actually F1.8.10 redress this disparity but at the cost of creating an entirely new set of inconsistencies.
In order to calculate the date of the Xiuhpohualli year-bearer one only needs to examine the Tonalpohualli count. The Julian year 1521 was contemporaneous to the year Yei Calli (Three House) in the Nahua-Mexica calendar, and the Tonalpohualli day of that designation recurs both 103 days before and 159 days after Ce Coatl in the divinatory count of that year. If F1.8.10 truly equates to the 13th of August then as Yei Calli days, either F1.3.8 (the 3rd of May) or F2.7.8 (the 18th of January) should be the year-bearer.
Indigenous accounts regarding the temporal location of the year-bearer vary as wildly as those of when the indigenous year began. In the case of the latter issue it is likely that disparate answers were given to a question that did not make a great deal of sense in terms of the Nahua-Mexica calendar, and responses may have been given in relation to the beginning of the Xiuhpohualli year, the Tonalpohualli year, the ilhuilhuiuh year, or any of the other definitions of a year by which hunters, farmers, politicians, or astronomers marked time. After all, our own seasons do not begin on January the first, and the financial year commences in April. Therefore the year-bearer date has been attributed to both the first day of the year bearing its name and to the last day. With this in mind, it is in theory only necessary to examine those days which might constitute the Yei Calli year-bearer in order to see which might be the most likely candidate. F1.3.8 (3rd of May) appears quite unsatisfactory as the beginning of any sort of year. F2.7.8 (18th of January) might be a more likely candidate being as it may be deemed to occur in the general temporal vicinity of one interpretation of the year's end, namely Izcalli (F2.7) - the first ilhuitl following the traditional six ilhuilhuiuh of frost referred to in the Florentine Codex (VII, 61):
"Cold comes once a year, in Ochpaniztli, it begins in Ochpaniztli. And for six feasts, six score days, the cold lasts. And then it ends, finishes, in Tititl. When that happened, they said: 'The frost has gone, now there will be sowing, it's sowing time, now earth will be planted, it's planting time; it's warm, mild, calm; the hour is good, right, at hand, imminent, here. They hurried and pressed on, restless, anxious, busy, worried, there was no let up; days would fly by. Anew they worked the fields..."
In these terms, Izcalli (which follows Tititl) would sound very much like a prime candidate for the beginning of a year. However, unfortunately that year would be Nahui Tochtli (Four Rabbit) - the one immediately following Yei Calli - and the year-bearer in question should in theory be one that falls at the end of a year rather than the beginning of the new one. At this juncture it therefore becomes apparent that something is very wrong with our dates and there is an impostor hiding amongst the correlation of 13th of August, Ce Coatl, and F1.8.10.
It should be recalled that F1.8.10 is derived from an attempt to adjust the indigenous records in line with those of their conquerors. It is therefore interesting to see what happens when the alteration is reversed, adjusting the Spanish account in line with the original indigenous date of F1.7.20. This operation shifts the 13th back to the 3rd of August (Julian), and although some might deem this an unacceptable distortion, it nevertheless produces a reading of the Nahua-Mexica calendar which at last makes sense. The TTTM correlation is honoured and the year-bearer suddenly falls upon F2.6.18.
Earlier on it was stated that the year-bearer date has been attributed to both the first day of the year bearing its name and to the last day. The most obvious objection to F2.6.18 as year-bearer is that the eighteenth day of an ilhuitl can hardly be considered its last day. However, it must be remembered that accounts given of when this day occurred were varied responses made across considerable barriers of both culture and language. As the last ilhuitl of the frost period, Tititl (F2.6) might be considered a worthy candidate for the end of an agricultural year, particularly as in this case it would define Izcalli (F2.7) as the first ilhuitl of the subsequent agricultural year, it being the first ilhuitl in which it was considered safe to begin planting without fear of seedlings being ruined by cold. Furthermore, if Tititl is the last ilhuitl of the year by these terms, it is therefore the eighteenth; and the eighteenth day of the eighteenth ilhuitl could certainly be considered to carry at least as much suitably symbolic resonance as, for example, the last day of the last ilhuitl (which in any case carries only series V day-signs and is therefore ineligible).
In conclusion, both indigenous testimony and simple mathematics appear to support F2.6.18 as year-bearer, thus at last establishing the Tonalpohualli count in relation to the TTTM correlation of the Xiuhpohualli calendar. This nevertheless raises serious questions regarding the dating of Cuauhtemoc's surrender to the 13th (rather than the 3rd) of August 1521, but considering the evidence against this date, it is very difficult to draw any conclusion other than that it is, for some presently unknown reason, in error.
Broader discussion of this particular problem is well beyond the scope of this narrative, and whilst it is a simple enough matter to reel off a list of ideas explaining how events of one date might have been set down as having occurred ten days later, it is not so simple to posit a suggestion which holds together under even the lightest scrutiny, let alone one which might be supported by objective evidence.
The siege of Tenochtitlan was a war of attrition which took its toll upon both sides to greater or lesser extents. Most accounts of this long drawn out battle are derived primarily from Hernan Cortés' letters to King Charles V of Spain and Bernal Díaz' History of the Conquest of New Spain. Although the former were composed more or less contemporaneous to the events described, Díaz only began writing the latter in 1568, and it was not definitively completed until 1576. Given that the 600 or so conquistadors involved in the siege would, it seems fair to assume, have been more concerned with staying alive than embarking on literary careers, and given that possibly not all of their number would have been entirely literate in the first place, the potential for European eyewitness accounts does not seem inspiring. This theoretically could limit the actual recording of the date 13th August to a small handful of individuals at best. All it might therefore take is one slip of either the hand or memory of an undoubtedly turbulent event in order to render an error which would then be repeated elsewhere and thus, by virtue of repetition, become authoritative.
On the other hand, it might be suggested that perhaps the indigenous accounts are either in error or have been deliberately tailored, and that a Mexica surrender on F1.8.10 was purposely recorded as having transpired ten days earlier. Given that the date by which the Tonalpohualli Ce Coatl aligns with F1.7.20 was apparently deemed an appropriate date for surrender in terms of its theological significance, there is a certain logic to this claim. However, it was recorded in Spanish accounts that the Mexica clearly knew that defeat was inevitable by this point, and that their continued lack of surrender seemed mystifying, particularly when one considers the terrible conditions of those still holding out in Tlatelolco. It is therefore highly unlikely that Cuauhtemoc would have bided his time in this manner, holding out for a particularly appropriate date upon which to surrender, only to attribute the act to a date occurring ten days earlier.
Alternately, 13th August is noted as being the feast day of Saint Hippolytus in the Catholic calendar. Saint Hippolytus the Martyr is historically distinguished for his near-puritanical devotion to Christian doctrine and for setting himself up in opposition to Rome in the belief that the ruling body of the church at the time was perhaps not so devout as it might be. Amongst what little is known of Saint Hippolytus is his vehement rejection of the idea of the Trinity on the grounds that only God himself can be the subject of worship. In other words, Saint Hippolytus might be seen as a fundamentalist, and as such his appeal may have been pronounced amongst the conquistadors as they fought for their lives in what must have seemed the most irredeemably heathen of alien territories. In context, if at some point a choice was made to alter the official date of the conquest, then whilst the feast day of Saint Hippolytus might only be one of a number of viable options, there is a certain symbolic symmetry in such a choice. As a rejection of pantheism, Hippolytus is as bold a statement as can be made given that he was intolerant of even the mild yet undeniably Christian pantheism of the Trinity. Attributing the victory to his feast day (whether deliberate or by error) might therefore be considered as akin to the construction of a mythic conception - the dramatic beginning of Christian (as opposed to indigenous) time in New Spain.
Whilst these ideas offered in account of a Spanish error might easily be pulled apart, they (arguably) seem the least unlikely of a number of possibilities; although for any merits they may be considered to possess, the central problem is that they are apparently beyond testing, and hence, true or not, equally beyond any serious possibility of validation. In the case of the Spanish August 13th versus the Mexican F1.7.20 it is unfortunate for our purposes that both suspects appear to possess near flawless alibis. There is no presently known answer to this problem, although that is quite different to suggesting that an answer to this problem does not exist, so for the time being the most sensible option would seem to be to focus on that which can at least be quantified - the Nahua-Mexica calendar itself.
It's work in progress, and comes at the end of a much longer essay on the nuts and bolts operation of the Tonalpohualli and Xiuhpohualli, but hopefully the relevant bits won't prove completely impenetrable. If anyone manages to read through all of it please feel free to award yourself 1 point.