Dog days sometimes used for the lethargic summer markets. Various computations of the dog days have placed their start anywhere from 3 July to 15 August and lasting for anywhere from 30 to 61 days. They may begin or end with the cosmical rising or heliacal rising of either Sirius in Canis Major or Procyon (the "Little Dog Star") in Canis Minor and vary by latitude, not even being visible throughout much of the Southern Hemisphere. Sirius observes a period of almost exactly 365¼ days between risings, keeping it largely consistent with the Julian but not the Gregorian calendar; nonetheless, its dates
The Sirius Mystery argue that the only way that the Dogon could have obtained what he understood to be accurate information on Sirius B was by contact with an advanced civilization; he considered alternative possibilities, such as a very ancient, advanced, and lost civilization that was behind the sudden appearance of advanced civilization in both Egypt and Sumeria. He personally found the theory of alien contact more convincing, but he did not claim certainty about it. Noah Brosch explained in his book "Sirius Matters" that cultural transfer could have taken place between 19th century French astronomers and Dogon tribe members during the observations