<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> <P> Many modern sources in the English - speaking world move this still earlier, from July 3 to August 11, ending rather than beginning with or centering on the reappearance of Sirius to the night sky . </P> <P> Although Sirius is the brightest proper star in the night sky, it is 8.7 light - years (8.23 × 10 km) away from Earth and has no effect whatsoever on the planet's weather or temperature . Although the star continues to return to the night sky in late summer, its position continues to gradually shift relative to the Sun and will rise in the middle of winter in about 10,000 years . </P>

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