| The epact thus continues to vary until at the end of nineteen years the new moons return as at first. |
| For, says he, because of the double epact that occurs on the 4th and 5th of April that lunation has only 29 days. |
| Divine names were also used to designate the 30 days of each month and of the 12 months of the year, plus five epact days, called gahānīg, to align the lunar with the solar year. |
| Thus, when the epact is 17, the new and full moons of March fall on the 13th and 28th. |
| On account of the solar equation S, the epact J must be diminished by unity every centesimal year, excepting always the fourth. |
| The epact is the number of days which must be added to a lunar year to complete a solar year. |
