CALIPPIC period, in Chronology, a series of seventy-five Calippic period seventy-six years, perpetually recurring; which clasped, the middle of the new and full moons, as its inventor Calippus, an Athenian, imagined, return to the same day of the solar year. Meton, a hundred years before, had invented the period, or cycle, of nineteen years; assuming the quantity of the solar year $365\frac{1}{4}$ days, $6h.\ 18'56''\ 50\frac{3}{4}''\ 41\frac{1}{4}'\ 34\frac{1}{2}''$; and the lunar month, $29d.\ 12h.\ 45'\ 47''\ 26\frac{3}{4}'\ 48\frac{3}{4}'\ 35\frac{1}{2}''$. But Calippus, considering that the Metonic quantity of the solar year was not exact, multiplied Meton's period by 4, and thence arose a period of 76 years, called the Calippic. The Calippic period, therefore, contains $27,759$ days; and since the lunar cycle contains $235$ lunations, and the Calippic period is quadruple of this, it contains $940$ lunations. This period began in the third year of the 112th Olympiad, or the 4384th of the Julian period. It is demonstrated, however, that the Calippic period itself is not accurate; that it does not bring the new and full moons precisely to their places; $8h.\ 5'52''\ 6s''$, being the excess of $940$ lunations, above 76 solar years; but brings them too late, by a whole day in 225 years.