|a calendar based on solar cycles|
any dating system based on the seasonal year of approximately 365 14 days, the time it takes the Earth to revolve once around the Sun. The Egyptians appear to have been the first to develop a solar calendar, using as a fixed point the annual sunrise reappearance of the Dog Star-Sirius, or Sothis-in the eastern sky, which coincided with the annual flooding of the Nile River. They constructed a calendar of 365 days, consisting of 12 months of 30 days each, with 5 days added at the year's end. The Egyptians' failure to account for the extra fraction of a day, however, caused their calendar to drift gradually into error
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