ETACTS, in chronology, the excease, of the solar month above the lunar synod ical month, and of the solar year above the lunar year of twelve synodical months. The °pacts, then, are either annual or monthly. Suppose the new moon to he on the 1st of January : since the lunar month is 29 days, 12 hours, 44 minutes, 3 seconds, and the month of January con tains 31 days; the monthly epact is I day, 11 hours, 15 minutes, 57 seconds. The an nual epact is nearly 11 days ; the Julian solar year being 365 days, 6 hours; • and the Julian lunar year 354 days, 8 hours, 48 minutes, 38 seconds. In the ordinary tables of the church calendar the epacts are given only for a single century ; but as the Gregorian calendar now in use de fines precisely the length of the year, tables, though somewhat more compli cated, have been formed, which show the epacts of every future year in all time to come. The epacts were invented by Luigi Lilio Ghiraldi, more frequently styled Aloysius Lilius, a physician of Na ples, and author of the Gregorian Calen dar, for the purpose of showing the days of the new moons, and thence the moon's age on any day of the year, and conse quently of regulating the Church festi vals. It is only in ecclesiastical compu
tations that the epaets are ever employed; in civil affairs the civilized portion of mankind hare long since laid aside the use of the lunisolar year, and regulated time entirely by the sun. In the calen dar of the Church of England, Easter and the other movable feasts are determined in the same manner as in the old Romish calendar, excepting that the golden nuin hers are prefixed to the days of the full moons, instead of the days of the new moons. The epacts are consequently not used. It is desirable that the custom of reckoning time by the moon, which had its origin in ignorant ages, were aban doned, and the civil year adopted for every purpose.