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Like other cultures around the world, the pre-contact American peoples developed methods of measuring time based on astronomical observations of the movements of heavenly bodies. Because the moon is easily visible and changes in appearance each day, it became the basis of calendars in many ancient societies. Solar calendars also arose for measuring the length of the day and year. Development of accurate calendars requires sophisticated mathematical calculations.

The system developed by the ancient Maya civilization was astronomically more accurate than the Julian calendar used in Europe at the time of the first encounters between early explorers and native cultures. The Maya used three interrelated calendars, two of which were used simultaneously. Like the Maya calendar, the Aztec calendar consisted of a ritual cycle of 260 days and a 365-day civil cycle.

This section provides examples of Maya and Aztec calendars and European texts from the fifteenth and sixteenth centuries that demonstrate the relationship between astronomical observation, mathematics, and the measurement of time.

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Miniature Altar

Many of the objects and scenes painted on Maya pottery deal with the concept of the creation of the universe. This group of four objects, three spheres and a flat disk, reflects the Maya concept of the beginning of time and symbolizes the hearth of creation at the center of the universe. Two dates appear on the disk, both of which are mythological, suggesting that the events associated with these dates are not of this world. The sphere with a jaguar is placed in the center. This assemblage may have been in the tomb of a royal woman who was given the three hearthstones and comal to accompany her on the journey into the other world.

Miniature “altar” with three spherical supports and painted glyphs. Guatemalan Lowlands. Maya, AD 200–600. Incised and red-painted marble. Jay I. Kislak Collection, Rare Book and Special Collections Division, Library of Congress (041.00.00)

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Finding the Past

In 1790, workers digging in a central plaza in Mexico City unearthed several huge carved stones. Among these was the Sun Stone, which was displayed with another find, a standing image of Coatlicue, the mother of the gods. Antonio León y Gamas’s publication provided the first study of the Sun Stone and the Coatlicue statue, both of which became symbols of growing Mexican nationalism.

Antonio de León y Gama (1735–1802). Descripción histórica y cronológica de las dos piedras en la plaza principal de México. Mexico: F. de Zúniga y Ontiveros, 1792. Jay I. Kislak Collection, Rare Book and Special Collections Division, Library of Congress (42.01.00, 042.01.01)

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Maya Dresden Codex

Displayed is a facsimile edition of the Dresden Codex, the most comprehensive source of Maya astronomy and calendar systems. It includes tables for predicting events and scheduling religious ceremonies that are based on the solar cycle and the cycles of the Moon and Venus. The codex was probably sent by Hernán Cortés to Emperor Charles V in 1519 and was acquired by the Royal Library in Saxony in Dresden in 1744.

Codex Dresdensis: Sächsische Landesbibliothek Dresden (Mscr. Dresd. R 310)/ Kommentar, Helmut Deckert, zur Geschichte der Dresdner Maya-Handschrift; Ferdinand Anders, die Dresdner Maya-Handschrift kodikologische Beschreibung. Graz, Austria: Akadem. Druck-u Verlagsanstalt, 1975. Jay I. Kislak Collection, Rare Book and Special Collections Division, Library of Congress (043.00.00, 043.00.09, 043.00.14, 043.00.19, 043.00.28, 043.00.41)

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Coiled Stone Rattlesnake With Day Sign

The Aztecs excelled in carving tightly coiled serpent sculptures from fine-grained stone. In such sculptures, the tall stacked coils are carefully cross-hatched for the scales, and the rattle tail is tucked at the base. Many of the sculptures have additional symbolic icons carved on their bases. On the flat bottom of this sculpture is a realistic long-eared rabbit image next to a dotted circle representing the numeral one. Rabbit is the eighth of the twenty Aztec day signs.

Coiled stone rattlesnake with day sign. Central Mexican Highlands. Aztec culture, AD 1400–1521. Gray volcanic basalt. Jay I. Kislak Collection, Rare Book and Special Collections Division, Library of Congress (044.00.00, 044.00.02). Photo ©Justin Kerr, Kerr Associates

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Positions of the Sun, Moon, and Planets

Cosmographia by German mathematician Petrus Apianus provides a layman’s introduction to subjects such as astronomy, geography, cartography, surveying, navigation, and mathematical instruments.  In this popular edition with changes by another noted mathematician, Gemma Frisius, movable paper instruments (volvelles) enabled readers to solve calendar problems and find the positions of the sun, moon, and the planets.  Apianus depicted the cosmos according to the  Ptolemaic system, which maintained that the sun revolved around the earth, a theory challenged by Nicolas Copernicus (1473–1543) in Apianus’s lifetime.

Petrus Apianus Apianus (1492–1552) and Gemma Frisius (1508–1555). Cosmographia, Petri Apiani . . . additis euisdem argumenti libellis ipsius Gemmaa Frisii. . . . Antwerp: Arnoldi Birckmanni, 1564. Rare Book and Special Collections Division, Library of Congress (045.00.00, 045.00.02, 045.00.03)

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Transition to the Gregorian Calendar

This book by the mathematician and astronomer Johannes Mueller, known as “Regiomontanus,” began the transition to the new, reformed Gregorian calendar.  Because Easter was based on the flawed Julian calendar introduced by Julius Caesar (100–44 BC), the day had gradually drifted away from its spring observance tied to the Jewish Passover. Regiomontanus died soon after being summoned to Rome by Pope Sixtus IV (reigned 1471 to 1484) to begin the reform. The calendar change was not achieved until 1582 under Pope Gregory XIII (reigned 1572 to 1585).

Johannes Mueller (1436–1476). [“Regiomontanus”] Calendarium [Calendar]. Nuremberg: 1474. Rosenwald Collection, Rare Book and Special Collections Division, Library of Congress (46.00.02, 046.00.03)

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Calendar Wheel

The Aztec calendar consists of 260 days (13 months, each containing 20 days), which determined the life of each Mexica (Aztec).  In Aztec society, priests consulted the calendar to determine auspicious days for weddings and other important events. The portion displayed here contains the symbols for each day and the sun, moon, and stars. Mariano Fernández Echeverría y Veytia drew these pictures of the calendar wheel in the early nineteenth century based on documents written prior to the Spanish conquest in 1521.

Mariano Fernández Echeverría y Veytia. Aztec Calendar Wheel from Historia del origen de las gentes que poblaron la América septentrional (History of the Beginnings of the People Who Settled North America). Early nineteenth-century facsimile manuscript. Peter Force Collection, Rare Book and Special Collections Division, Library of Congress (047.00.00, 47.00.02, 047.00.03)

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