Can we therefore believe that the Egyptians before this period were ignorant of the bissextile intercalation?
This fourth year was denominated bissextile, because the sixth day before the Kalends of March was reckoned twice.
The bissextile is known to have been used by the Mayas, Tzendals, and Quichés, and it was probably common.
The fourth year was bissextile, and the dominical letters were F, E; the following year D, and so on.
1580s (n.); 1590s (adj.), in reference to Roman leap year, from Late Latin (annus) bissextilis "leap year," literally "the twice sixth-day," because the sixth day before the Calends of March was doubled.