The Zapotec developed a calendar and a special system of writing. This system has a separate glyph for each of the syllables of the language. It is one of several candidates thought to have been the first writings system of Mesoamerica. It is the predecessor of the writing systems developed by the Maya, Mixtec, and Aztec civilizations. Currently there is some debate if Olmec symbols, dated to 650 BC, are actually a form of writing which is older than the earliest Zapotec writing dated to about 500 BC.