EPACT. - From the Greek ἐπάγειν (to add), it is the number that indicates, from year to year and at a determined moment, the excess of days of the solar year over the lunar year.

This excess increases by 11 units each year: so that the same new moon falls 11 days earlier after 1 year, 22 after 2 years, 33 after 3, and so on. In practice, however, every three years the gap is partly canceled by the subtraction of 30 days, which form a supplementary month (endolional [v]), so that the coincidence between the solar year and the lunar year is re-established after 19 years. On the basis of this principle the e. is placed in relation to the golden number and indicated in certain tables, which however do not have perpetual validity, inasmuch as the excess mentioned above is not exactly 11 days. From 1900 to the end of 2199, the following table is in force:

golden number	epact	golden number	epact
1	20	11	19
2	10	12	no epact
3	21	13	11
4	2	14	22
5	13	15	3
6	24	16	14
7	5	17	25
8	16	18	6
9	27	19	17
10	8

The computation of the e. is generally begun on 1 January, so that the figures in question are valid for the whole duration of the year: nevertheless some computists had it run from another date, especially from 1 September. See also EASTER.

Bibliography3 works

BIBL.: E. Brinckmeier, Praktisches Handbuch der historischen Chronologie, 2nd ed., Berlin 1882, pp. 76-80, 102, 132; A. Guy, Manuel de diplomatique, Paris 1894, pp. 140-51; H. Grosfand, Abris der Chronologie des deutschen Mittelalters und der Neuzeit, 2nd ed., Leipzig-Berlin 1912, pp. 19-21.

Alessandro Pratesi

@incollection{ec5_epatta, author = {Pratesi, Alessandro}, title = {Epatta}, booktitle = {Enciclopedia Cattolica}, volume = {V}, pages = {405}, note = {Cited by column}, publisher = {Ente per l’Enciclopedia Cattolica e per il Libro Cattolico}, address = {Città del Vaticano}, year = {1950}, url = {https://azioneromana.com/article/epatta} }

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Epact

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