Fabricio Duarte's List: History 201

• a 260-day divinatory calendar important in Mesoamerican cosmology and
• 365-day year that structured community events
• By 36 BCE, lowland Mayans or Epi-Olmecs had made a more  elaborate adjustment—the long count
• under-went very ancient changes in pronunciation, probably well before 600  BCE

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• They say that this threatening planet on a 3600-year orbit was discovered by the  ancient Mesopotamians, who named it Nibiru, and it was known also to the Mayans,  who associated it with the end of their calendar "long count" in December 2012.