Complete text (abstract only):
The Gregorian Calendar is an adjustable cyclical calendar which takes account of the solar and lunar movements; it is based on the so called Callippian cycle: 76 tropical years = 940 synodical months = 27759 days. (The name goes back to the Greek astronomer Callippos from Kyzikos who first used this cycle for time measuring purposes in 330 B.C.). In the Gregorian Calendar, such a cycle runs for at least one century, sometimes two centuries without any disturbances. At certain turns of the century there occur alterations due to leap years; however, these alterations do not occur at a fixed point in time, but are flexible enough to allow for the calendar to be adjusted to the changing course of the Sun and the Moon.
The purpose of my poster was to present the Callippian cycle in the Gregorian Calendar as it is in force today, to illustrate how it was discovered and to discuss its structure in some detail. My aim is to establish an algebraic relation between the well-known solar dates and the lunar dates, the latter remaining almost unknown, although they have been an integral part of the Gregorian Calendar for over 400 years.
I would like to point out that this ingenious system, which has been achieved with great efforts over the centuries, may now be jeopardised by a recent proposal of the World Council of Churches (March 1997), which, albeit well-meant, should be examined very thoroughly.
Written in Bonn on Sunday, March 15, 1998 = Adaru II 17 1997
Please note: The printed version contains an error introduced by the editors. Instead of »My aim was to establish an algebraic relation ...« the phrase should read »My aim is to establish an algebraic relation ...«. The editors apologize for this.
Bibliographical details:
Heiner Lichtenberg: The decoding of the Callippian Cycle in the Gregorian Calendar for the period between 1900 and 2099. In: Peter Brosche, Wolfgang R. Dick, Oliver Schwarz, Roland Wielen (Eds.): The Message of the Angles - Astrometry from 1798 to 1998. Proceedings of the International Spring Meeting of the Astronomische Gesellschaft, Gotha, May 11-15, 1998. (Acta Historica Astronomiae ; 3). Thun ; Frankfurt am Main : Deutsch, 1998, p. .
Html-Version: Wolfgang R. Dick. Created: 21 Jan 1999