epact

American  

[ee-pakt] / ˈi pækt /

noun

1. the difference in days between a solar year and a lunar year.

2. the number of days since the new moon at the beginning of the calendar year, January 1.

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epact British  

/ ˈiːpækt /

noun

1. the difference in time, about 11 days, between the solar year and the lunar year

2. the number of days between the beginning of the calendar year and the new moon immediately preceding this

3. the difference in time between the calendar month and the synodic month

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Etymology

Origin of epact

1545–55; < Late Latin epacta < Greek epaktḗ, noun use of feminine of epaktós added, equivalent to ep- ep- + ag ( ein ) to lead + -tos verbid suffix

Example Sentences

There only needs to add together the epact, number of the month, and day of the month; the sum of which, if under thirty, gives the moon's age--the excess, if over.

From The History of Sumatra Containing An Account Of The Government, Laws, Customs And Manners Of The Native Inhabitants by Marsden, William

The annual epact is nearly 11 days; the solar year being 365 days, and the lunar year 354.

From The New Gresham Encyclopedia Volume 4, Part 2: Ebert to Estremadura by Various

The value of L is always given by the formula for the dominical letter, and P and l are easily deduced from the epact, as will appear from the following considerations.

From Encyclopaedia Britannica, 11th Edition, Volume 4, Part 4 "Bulgaria" to "Calgary" by Various

Thus we have the epact, or age of the Calendar moon at the beginning of the year.

From A Budget of Paradoxes, Volume I by Smith, David Eugene

It should be borne in mind that the epacts are obtained by successively adding eleven to the epact of the former year, and rejecting thirty as often as the sum exceeds or equals that number.

From Our Calendar by Packer, George Nichols