Earliest evidence of Maya calendar found inside Guatemalan pyramid. A glyph representing a day called “7 Deer” on mural fragments dating from the third century BC found inside the ruins of a pyramid in Guatemala marks the earliest-known use of the Maya calendar, one of this ancient culture’s renowned achievements. The fragments were found at the San Bartolo archeological site in the jungles of northern Guatemala, which gained fame with the 2001 discovery of a buried chamber with elaborate and colorful murals dating to about 100 BC depicting Maya ceremonial and mythological scenes, researchers said on Wednesday. The pieces with the “7 Deer” glyph were unearthed inside the same Las Pinturas pyramid where the still-intact later murals were located. As was the case with this structure, the Maya often built what initially were modest-sized temples, then constructed ever-larger versions atop the earlier ones. This pyramid eventually reached about 100 feet (30 meters) tall.