Aztec calendar, 1699-1700 Engraved by Giovanni Francesco Gemelli Careri (1651-1725), who was a seventeenth-century Italian adventurer and traveler. This calendar appears in "Voyage du Tour du Monde" (1719) by Careri. The tonalpobualli, or sacred calendar, ruled the life of each Mexica (Aztec) and was consulted on all important occasions well before the early-16th-century Spanish conquest. It was made up of 260 days, or 13 months of 20 days each.