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 that the Dogon probably gained from Europeans to some extent resembles the facts about Sirius, the presumed original Dogon knowledge on the star is very far from the facts. Ridpath concluded that the information that resembles the facts about Sirius was probably ascertained by way of cultural contamination. More recent research suggests that the contaminator was Griaule himself. Astronomer Carl Sagan touched upon the issue in his book "Broca's Brain" (1979), seeing problems in Temple's hypothesis. As an example, Sagan believes that because the Dogon seem to have no knowledge of another planet beyond Saturn which has rings, that their