A dot is one, a bar is five, a shell is zero.

Maya civilization grew from independent states with roots around 1000 BCE, across what is now Mexico, Guatemala, Belize, Honduras and El Salvador.1 Its Classic period, about 250–900 CE, was the peak of Maya architecture, art, writing and population, with great kingdoms such as Tikal in Guatemala and its rival Calakmul in Mexico.1

Spanish conquest of the region began in 1524 CE, and the last independent Maya state, at Tayasal, fell in 1697 CE.1

Maya numbers use three symbols: a shell for zero, a dot for one and a bar for five. Numbers are stacked in places of twenty, with the ones at the bottom: twenty is a single dot above a shell.2 For the calendar, priests used a modified count where the second place stands for 360 days instead of 400, close to the length of a year.2

The Maya based their calendars on the cycles of the Sun, the Moon and Venus. The best-known are the Haab, the Tzolk'in, the Calendar Round and the Long Count.3 The earliest Long Count date yet found is at Tikal, July 8, 292 CE.1

The Maya were one of the few peoples to come up with a zero on their own. Read how the world found zero.

Maya writing combines symbols for whole words with symbols for syllables.3 The earliest evidence of it, at El Portón, dates to about 400 BCE, and rulers carved royal histories and creation stories on monuments.1 The script stayed in use until about the end of the 17th century.4

Only four Maya books, called codices, survive from before the Spanish conquest. One of them, the Grolier Codex, was confirmed in 2016 as genuine and likely the oldest surviving manuscript of the ancient Americas, dated to the 13th century.5

Most Classic Maya cities declined between about 800 and 900 CE, through drought, warfare, overpopulation and other pressures.1 But the Maya did not vanish: more than seven million Maya live in their homelands and around the world.3 About 30 Mayan languages are still spoken.6

A Maya number is read by where each symbol sits: the same dot means one at the bottom and twenty one level up.2 A QR code works the same way. Every square is just dark or light; its position decides what it means.