EPACTS (Gr. aadditions”, in ecclesiastical chronology, a set of 19 numbers used for fixing the date of Easter and other Church festivals, by indicating the age of the moon at the be ginning of each civil year in the lunar cycle At the reformation of the calendar in 1582 it was found that the Golden Numbers could no longer by themselves serve the purpose of adjusting the double reckoning by lunations and by the trop'cal or true year; and thus, instead of adopting the more rational com putation, the Roman Church devised the arti ficial and involved method of epacts. The main point to determine is the age of the moon (in entire days) at the beginning of each civil year, or the number of days between the end of the ecclesiastical year in December and the first January succeeding. Thus, subtracting 354 days (12 lunations) from 365, we should have 11 days for the first annual epact, then 22 for the year following, then 3, 14, 25, 6, 17, 28, 9, 20, I, 12, 23, 4, 15, 26, 7, 18 and 29; the series of 19 numbers being obtained in succession by add ing 11, and when the sum exceeds 30, subtract ing that number. This illustration, however, is simpler than any actual case, by reason of the leap-years, which require 12 to be added for the following epact, and of the fact that no lunation is exactly 30 days long. When the lunar cycle
of 19 years is completed, the epacts recur again in the same order. In the Anglican reckoning, as distinguished from the Roman, it is note worthy that the Gregorian epact for any year is the same as the Julian epact for the year preceding, owing to the coincidence that 11, the number of days lost on the Julian account before the English Parliament adopted the re formed calendar (q.v.), is also the number of days between the lunar and the solar years.
/ The epact determines by subtraction the date of the first new moon in anuary; then by adding 29 and 30 alternately the successive new moons throughout the year are assigned to their re spective dates. Consult Clams, C.,
Calendarii a Gregorio XIII P. M. Restituti Ex plicatio etc.' (Rome 1603) ; Butcher, J. G., and Butcher, S. H., editors, (The Ecclesiastical Calendar: Its Theory and Construction' (Dub lin 1877) ; De Morgan, A., (The Book of Almanacs' (London 1871) • Seabury, S.,