What is "sothic cycle"

The Sothic cycle, or Canicular period, is a period of 1,461 ancient Egyptian years (of 365 days each) or 1,460 Julian years (averaging 365.25 days each). During a Sothic cycle, the 365-day year loses enough time that the start of the year once again coincides with the heliacal rising of the star Sirius (the Latinized name for Greek Σείριος, a star called Sopdet by the Egyptians, in Greek transcribed as Sothis; a single year between heliacal risings of Sothis is a Sothic year). The rising occurred within a month or so of the beginning of the Nile flood, and it was a matter of primary importance to the agricultural society. It is believed that Ancient Egyptians followed both a 365-day civil calendar and a lunar religious calendar.