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 Culture". One unproven aspect of the reported Dogon knowledge of the Sirius system is the assertion that the Dogon knew of another star in the Sirius system, Emme Ya, or "larger than Sirius B but lighter and dim in magnitude." A dynamical study published in 1995, based on anomalous perturbations of Sirius B (suggestive of the star being gravitationally influenced by another body) concluded that the presence of a third star orbiting Sirius could not be ruled out. An apparent "third star" observed in the 1920s is now confirmed as a background object, something previously suggested by Holberg in 2007: