In the

Aztec The Aztecs () were a Mesoamerican culture that flourished in central Mexico in the post-classic period from 1300 to 1521. The Aztec people included different Indigenous peoples of Mexico, ethnic groups of central Mexico, particularly those g ...

culture, the

Nahuatl Nahuatl (; ), Aztec, or Mexicano is a language or, by some definitions, a group of languages of the Uto-Aztecan language family. Varieties of Nahuatl are spoken by about Nahua peoples, most of whom live mainly in Central Mexico and have smaller ...

word refers to a period of five

intercalary Intercalation may refer to: *Intercalation (chemistry), insertion of a molecule (or ion) into layered solids such as graphite *Intercalation (timekeeping), insertion of a leap day, week or month into some calendar years to make the calendar follo ...

days inserted between the 360 days labeled with numbers and day-names in the main part of the Aztec seasonal calendar. Their location was roughly around 5–18 April every Gregorian year.

Etymology

The word means "they fill up in vain". Spanish lexicographers glossed it as , "wasted days". The interpretation is that the Mexicas considered the days unlucky, and most activities (including even cooking) were avoided as far as possible during the period; however this is interpretation is contested. A more recent minority opinion is that people used the 5 day period to reflect over the past year, and that this contemplation often included a period of fasting.

Position in Aztec calendar

Each of the 18 Aztec "months" had 20 days, for a total of 360 days. The accounted for the remaining 5 whole days in the nearly 365 ¼ day

tropical year A tropical year or solar year (or tropical period) is the time that the Sun takes to return to the same position in the sky of a celestial body of the Solar System such as the Earth, completing a full cycle of seasons; for example, the time fro ...

(365.2422, actual). There were no "

leap day February 29, also known as leap day or leap year day, is a date added to leap years. A leap day is added in various solar calendars (calendars based on the Earth's revolution around the Sun), including the Gregorian calendar standard in mo ...

s" or "

leap year A leap year (also known as an intercalary year or bissextile year) is a calendar year that contains an additional day (or, in the case of a lunisolar calendar, a month) added to keep the calendar year synchronized with the astronomical year or s ...

s" per-se, so over the course of 52 calendar years of 365 days each, the calendar accumulated a deficit of 13 days, which the

Julian calendar The Julian calendar, proposed by Roman consul Julius Caesar in 46 BC, was a reform of the Roman calendar. It took effect on , by edict. It was designed with the aid of Greek mathematicians and astronomers such as Sosigenes of Alexandr ...

(for example) accommodates by adding

s once every four years. According to Tunnicliffe (1979) the Aztecs dealt with the remaining fractional-day discrepancy with the true tropical year length by adding a (13 days) after each bundle of 52 years. The 13 days were not considered unlucky, but they were not labeled using the numbers and symbol combinations used for the rest of the Aztec calendar.

References

{{reflist, 25em, refs= {{cite book , first=Rafael , last=Tena , year=2008 , title=The Mexica Calendar and the Chronography , publisher={{lang, es,

Instituto Nacional de Antropología e Historia The Instituto Nacional de Antropología e Historia (INAH, ''National Institute of Anthropology and History'') is a Mexican federal government bureau established in 1939 to guarantee the research, preservation, protection, and promotion of the ...

– CONACULTA {{cite book , last=Tunnicliffe , first=K.C. , year=1979 , title=Aztec Astrology , place=Romford, UK , publisher=L.N. Fowler , oclc=5355273 , isbn=9780852433584 This work shows how the {{lang, nci, nēmontēmi days are calculated for each current year (around 5–10 April every year). Aztec mythology and religion Aztec calendars