Dionesian PERIOD, or Villorian Period, a system of 532 lunar-solar and Julian years; which being elapsed, the characters of the moon fall again upon the same day and feria, and revolve in the same order, according to the opinion of the ancients.
This period is otherwise called the great paschal cycle, because the Christian church first used it to find the true time of the pascha or easter. The sum of these years arise by multiplying together the cycles of the sun and moon.
Hipparchus's PERIOD, is a series of 304 solar years, returning in a constant round, and restoring the new and full moons to the same day of the solar year, according to the sentiment of Hipparchus. This period arises by multiplying the Calippic period by four.—Hipparchus assumed the quantity of the solar year to be 365 days 5 hours 55' 12"; and hence concluded, that in 104 years Calippus's period would err a whole day. He therefore multiplied the period by four, and from the product cast away an entire day. But even this does not restore the new and full moons to the same day throughout the whole period; but they are sometimes anticipated 1 day 8 hours 23' 29" 20". See ASTRONOMY, n° 14.
Julian PERIOD. See JULIAN.