Sefer Evronot (Book of Intercalations) by Eliezer Beilin, edited by Meir ben Joshua Hammelburg, Offenbach:1722

42 leaves (7 7/8 x 6 1/4 in.; 195 x 160 mm). f.4 misbound between ff.8-9. Illustration to title page and ff. 23r-24v.; additional foliation in pencil; complete with all volvelles on f.25r [2 pcs.], f.25v [3pcs.], f.28r [3 pcs.] and f.28v. [3 pcs.] Soiled; corners rounded; Half-calf over decorated paper boards.

Joshua Straus, Calculating Celestial Cycles, Courses and Conjunctions: An Introduction to Sifrei Evronot , Washington University: 2006; Barry B. Levy, Planets, Potions and Parchments: Scientifica Hebraica from the Dead Sea Scrolls to the Eighteenth Century, Montreal: 1990.

Sefer Evronot is a work containing the information and rules necessary for the fixing of the Jewish calendar. These calculations determine the lengths of individual months, the scheduled intercalation of leap years, the solstices and equinoxes that begin each of the four seasons, and by extension, the dates of all holidays of the Jewish liturgical year.  Unlike other manuals which rely exclusively on charts and tables, this volume makes ingenious use of multiple spinning dials that serve as circular slide rules and aid in the elaborate computational exercises.

A Sefer Evronot, first ascribed to Eliezer ben Jacob Belin Ashkenazi, was printed in Lublin in 1614, with subsequent editions appearing until the 19^th century.  However, Belin's work represents an assembling of previous sources into a consolidated text, as stated in the author's introduction: "we have searched in new books as well as old, one by one, in order to find the calculation of the lunations, remainders and the determination of plene and defective years and arranged it in the proper and correct order."

Jews in the late Middle Ages and early Modern period, particularly those whose livelihood was bound up in commercial trade, were required to be able to effectively interact with their Christian neighbors. This necessitated a working knowledge of the general outlines of the Christian calendar in addition to their own. Accordingly, this volume includes Luah Hehagaot, a chart containing the months and fixed saints' days of the Christian ecclesiastical year and a brief accompanying text commonly attributed to Meir ben Joshua Hammelburg.