About 2 chapters and a bit into Harbinger of the Storm, and already struggling with continuity issues. For starters, I know I worked out all the dates for Servant of the Underworld using my trusty Aztec calendar–unfortunately, I lost the file somewhere in transit between my old laptop and the new mac. Bottom line, I’m rereading the manuscript and hoping for clues that will tell me when exactly everything was taking place…

Also, fun activity of the day: work out maths. If you know the European year for something (say, 1481), and the Aztec sacred day for something in the same year (say, One Movement), what is the European date? It’s trickier than it sounds, mostly because the Aztec system is so weird.

For starters, you have two calendars: one is the solar year, which is 365 days, and, like in most civilisations, is separated into months, in this case eighteen months of twenty days plus five “empty days”.

Then, overlapping it, you have the sacred or religious calendar, which is 260 days long. This is the one that has the cool day names like Seven Serpent, Two Jaguar and so on. It’s the one in which the divinatory records were made, and hence the one in which a lot of the dates come from. It doesn’t really have months: “Serpent” is a daysign that recurs every twenty days. The calendar goes something like this: you have thirteen numbers, and twenty day signs. You increment both simultaneously until you run out of numbers, wrap the numbers around to 1 while continuing to number the day-signs to 20, then wrap that around to 1, while continuing to count the day numbers to 13, and so on…
Simply put, if I use a second set of numerals for the day signs instead, the count goes 1-1, 2-2, … 13-13, 1-14, 2-15,… 7-20, 8-1, etc.
In full names, it goes all over the place: One Crocodile, Two Wind, Three House… Thirteen Reed, One Jaguar. Two Eagle, … Seven Flower, Eight Crocodile… It’s not quite as disorganised as it looks like: the key is not counting the months, but going instead for the trecenas, the groups of thirteen days that go from one to thirteen (in the example above, the first trecena runs from One Crocodile to Thirteen Reed, and the second trecena starts on One Jaguar).

Now, the Aztec Calendar lets you enter a date in Julian or Gregorian calendar, and gives you the Aztec date for this day (in this case, the solar year, the trecena, and the sacred day). The key is then working out where you are in the year, and how far ahead you have to advance to reach your goal of day One Movement in the year 1481 (which is solar year Two House). In practise, I worked out the trecena for the day One Movement, and how distant it was from the trecena for my random date (basically, for the maths geeks, count in increments of 13 modulo 20, which gives you the number of trecenas, ie the number of days, which you then convert back into months).

If that sounds painful and confusing, that’s because it is. But it worked–I now know where in the year the book is supposed to be set 🙂