Enciclopedia Cattolica

CICLO SOLARE

Solar Cycle

Volume III · p. 924 · 1949

English translation · Testo originale italiano

Image from page 924
Image from page 924

Machine translation of the 1948–1954 Italian original. The original text is authoritative.

SOLAR CYCLE. – This is the name improperly given to a period of 28 solar years (Latin *circulus solis*, French *cycle solaire*, German *Sonnenzyklus*), after which the succession of the days of the week again corresponds exactly to the dominical letters A–G, conventionally assigned to the progressive order of the days of the week that begin the year.

For example, if a given year begins on a Sunday, with 1 January called A, 2 January B, 3 January C, and so on, the series A–G (Sunday–Saturday) will again correspond to the days 1–7 January after 28 years. The solar cycle, which in reality has no connection with the course of the sun, was widely used in the Middle Ages for the direct determination of the “dominical letter” (v.) and for the calculation of Easter.

Bibl.: E. Brinckmeier, *Praktisches Handbuch der historischen Chronologie... des Mittelalters*, Berlin 1882, pp. 68–69; A. Giry, *Manuel de diplomatique*, Paris 1894, pp. 134–37; H. Grotefend, *Abriss der Chronologie des deutschen Mittelalters und der Neuzeit* (Grundriss der Geschichtswissenschaft, ed. by A. Meister, I, III), 2nd ed., Leipzig–Berlin 1912, pp. 7–10.