<P> Because "July is typically one of the quietest months of the year for stock trading", the term is sometimes used for the lethargic summer markets . </P> <P> 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 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 3651⁄4 days between risings, keeping it largely consistent with the Julian but not the Gregorian calendar; nonetheless, its dates occur somewhat later in the year over a span of millennia . </P> <P> In antiquity, the dog days were usually reckoned from the appearance of Sirius around 19 July (Julian) to relieving rains and cool winds, although Hesiod seems to have counted the worst of summer as the days leading up to Sirius's reappearance . </P> <P> In Anglo - Saxon England, the dog days ran from various dates in mid-July to early or mid-September . Canonical "dog daies" were observed from July 7 to September 5 in the 16th - century English liturgies . They were removed from the prayer books at the restoration of the monarchy in 1660 and their term shortened to the time between July 19 and August 20 . During the British adoption of the Gregorian calendar in 1752, they were shifted to July 30 to September 7 . </P>

Where did the term dog days of summer