CONCURRENT DAYS (CONCORRENTI). - Conventional figures used by computists to determine which day of the week corresponds to the beginning of each year, and therefore to establish when Easter falls.

The figure of the concurrents, also called "solar epacts," or "major epacts," referred to a given year, indicates how many days have elapsed between the last Sunday of the preceding year and the beginning of the new year. Since Easter is regulated by the spring equinox, the relationship in which the concurrents stand to March 24 has been calculated: taking into account that from the beginning of the year to that date 82 days elapse (83 in leap years), that is, 11 times 7, plus 5 days, March 24 will fall on a day of the week that is shifted by 5 units relative to that of January 1 — that is, if in a given year January 1 falls on a Sunday, March 24 will fall on a Friday, and so on. And since the dominical letters (v. LETTERA DOMENICALE) correspond to the concurrents in the following way: A=6, B=5, C=4, D=3, E=2, F=1, G=7, between the concurrents and the day of the week on which March 24 falls there will be the following relationship:

Concurrents	1	2	3	4	5	6	7
dominical letter	F	E	D	C	B	A	G
day of the week on January 1	Tue.	Wed.	Thu.	Fri.	Sat.	Sun.	Mon.
and on March 24	Sun.	Mon.	Tue.	Wed.	Thu.	Fri.	Sat.

In leap years the figure of the concurrents naturally advances by one unit on February 29.

Bibliography3 works

BIBL.: E. Brinckmeier, Praktisches Handbuch der historischen Chronologie... des Mittelalters, Berlin 1882, pp. 70-73; A. Giry, Manuel de diplomatique, Paris 1894, pp. 137-39; H. Grotefend, Abriss der Chronologie des deutschen Mittelalters und der Neuzeit (Grundriss der Geschichtswissenschaft, ed. von A. Meister, I, III), 2nd ed., Leipzig-Berlin 1912, p. 21.

Alessandro Pratesi

@incollection{ec4_concorrenti, author = {Pratesi, Alessandro}, title = {Concorrenti}, booktitle = {Enciclopedia Cattolica}, volume = {IV}, pages = {197}, 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/concorrenti} }

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