- the difference in days between a solar year and a lunar year.
- the number of days since the new moon at the beginning of the calendar year, January 1.
Origin of epact
Examples from the Web for epact
The Epact is the number of days which must be added to a lunar year to complete a solar year.Time and Time-Tellers
James W. Benson
The epact thus continues to vary until at the end of nineteen years the new moons return as at first.Time Telling through the Ages
Harry Chase Brearley
Thus we have the epact, or age of the Calendar moon at the beginning of the year.
Thus, when the epact is 17, the new and full moons of March fall on the 13th and 28th.
During those few and sombre days which represented the epact of the dying year, Martin Grimbal returned to Chagford.Children of the Mist
- the difference in time, about 11 days, between the solar year and the lunar year
- the number of days between the beginning of the calendar year and the new moon immediately preceding this
- the difference in time between the calendar month and the synodic month
Word Origin and History for epact
1550s, "number of days by which the solar year exceeds a lunar one of 12 moons;" also "number of days into the moon on which the solar year begins;" from French épacte (12c.), from Late Latin epacta "an intercalary day," from Greek epaktos, literally "brought in, inported," verbal adjective of epagein "to intercalate, add, bring forward," from epi "on" (see epi-) + agein "to bring, to lead" (see act (v.)).