from The American Heritage® Dictionary of the English Language, 5th Edition.

  • noun The period of time necessary to bring the solar calendar into harmony with the lunar calendar.

from The Century Dictionary.

  • noun The excess of a solar over a lunar year or month. Hence, usually A number attached to a year by a rule of the calendar to show the age, in days completed and commenced, of the calendar moon at the beginning of the year—that is, on January 1st in the Gregorian, Victorian, and early Latin calendars, or March 22d in the Dionysian calendar, or old style.

from the GNU version of the Collaborative International Dictionary of English.

  • noun (Chron.) The moon's age at the beginning of the calendar year, or the number of days by which the last new moon has preceded the beginning of the year.
  • noun the excess of the solar year over the lunar year, -- being eleven days.
  • noun the excess of a calendar month over a lunar.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

  • noun the time (number of days) by which a solar year exceeds twelve lunar months; it is used in the calculation of the date of Easter


from The American Heritage® Dictionary of the English Language, 4th Edition

[French épacte, from Late Latin epacta, from Greek epaktē (hēmera), intercalary (day), feminine of epaktos, brought in, inserted, from epagein, to bring in, introduce : ep-, epi-, epi- + agein, to lead; see ag- in Indo-European roots.]


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  • epact 11 days that never were

    January 14, 2007

  • A period added to harmonize the lunar with the solar calendar.

    May 12, 2008

  • epact (n): an electronic international treaty

    May 15, 2008

  • To find the Epact: Divide the given year by 19; multiply the remainder by 11, and the product will be the Epact, if it does not exceed 29; but if it does, divide the product by 30, and the last remainder will be the Epact.

    Example: Epact for 1846. 1846, divided by 19, gives 97 for the quotient, and 3 for the remainder, which is multiplied by 11, gives 33; this, divided by 30, gives the quotient 1, and the remainder 3; which is the Epact for the year 1846.

    See Golden Number for a similar formula for finding the Epact.

    September 24, 2008

  • What is this used for? It seems quite useless.

    September 26, 2008