fuzzyworld

when-am-i / files / src / data / calendars / aztec.json

aztec.json

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9c2d2d06 2026-06-21 Pavel Safronov1{
2 "region": {
3 "name": "Aztec Empire (central Mexico)",
4 "geo": {
5 "type": "Polygon",
6 "coordinates": [
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f277378b 2026-06-24 Pavel Safronov8 [
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9c2d2d06 2026-06-21 Pavel Safronov72 ]
73 ]
74 }
75 },
76 "eras": [
77 {
78 "name": "Xiuhpōhualli (365-day solar calendar)",
79 "start": "1325-01-01",
80 "end": "1521-08-13",
81 "calendar": "Aztec Xiuhpōhualli",
82 "usedBy": "the Aztec/Mexica",
83 "description": "The Mexica civil calendar: 18 months (veintenas) of 20 days each, plus a 5-day unlucky period (nēmontemi), totaling 365 days. It has no continuous numbered year — a year is named only by its position in the 52-year cycle (see the year-bearer era below). The exact day the year began is disputed among colonial-era sources (accounts place it anywhere from February to March), with no leap-day mechanism to keep it aligned to the solar year, so this dataset does not attempt a precise day-level conversion. Scoped here to the imperial period, from the traditional founding of Tenochtitlan (1325) to the fall of the city to the Spanish (13 August 1521), though Mesoamerican communities continued using related 365-day calendars informally long afterward.",
84 "sources": [
85 "https://en.wikipedia.org/wiki/Xiuhp%C5%8Dhualli",
86 "https://en.wikipedia.org/wiki/Aztec_calendar",
87 "https://en.wikipedia.org/wiki/Tenochtitlan"
88 ]
89 },
90 {
91 "name": "Year-bearer (52-year cycle)",
92 "start": "1325-01-01",
93 "end": "1521-08-13",
94 "calendar": "Aztec/Mexica year-bearer",
95 "usedBy": "the Aztec/Mexica",
96 "description": "Years were named by combining one of four day-signs — Ācatl (Reed), Tēcpatl (Flint), Calli (House), Tōchtli (Rabbit) — with a number 1–13, repeating every 52 years (the xiuhmolpilli, 'Calendar Round'); there is no Aztec equivalent of the Maya Long Count, so no absolute year number exists. The cycle is anchored here at 1519 CE = '1 Ācatl', documented because of its association with the Cortés-arrival/Quetzalcōātl-return prophecy, cross-checked against the 1507 New Fire Ceremony at the Hill of the Star, recorded as '2 Ācatl'.",
97 "sources": [
98 "https://en.wikipedia.org/wiki/Aztec_calendar",
99 "https://en.wikipedia.org/wiki/Spanish_conquest_of_the_Aztec_Empire",
100 "https://en.wikipedia.org/wiki/New_Fire_ceremony"
101 ]
102 },
103 {
104 "name": "Tōnalpōhualli (260-day ritual calendar)",
105 "start": "1325-01-01",
106 "end": null,
107 "calendar": "Tōnalpōhualli",
108 "usedBy": "the Aztec/Mexica and their descendants",
109 "description": "A 260-day cycle combining 20 day-signs with 13 numbers (e.g. a person named '5 Lizard' for their birth-day), used for divination, naming, and ritual timing rather than tracking elapsed years — it has no year count at all. Predates and outlasted the empire; related 260-day count calendars remain in ceremonial use among some Mesoamerican communities today, so this era is left open-ended.",
110 "sources": [
111 "https://en.wikipedia.org/wiki/T%C5%8Dnalp%C5%8Dhualli",
112 "https://en.wikipedia.org/wiki/Aztec_calendar"
113 ]
114 }
115 ]
f277378b 2026-06-24 Pavel Safronov116}