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
Sirius the star when rising left the viewer with the impression that it was red. To the naked eye, it often appears to be flashing with red, white and blue hues when near the horizon. With an apparent magnitude of −1.46, Sirius is the brightest star system in the night sky, almost twice as bright as the second brightest star, Canopus. From Earth, Sirius always appears dimmer than Jupiter and Venus, as well as Mercury and Mars at certain times. Sirius is visible from almost everywhere on Earth, except latitudes north of 73° N, and it does not rise very high