A fascinating 18th century Italian perpetual calendar, constructed of manuscript and engraving on paper tacked to wood, with wood and board volvelles, with numerous concentric circles for displaying or calculating the Dominical Letter system, the epacts and phases of the moon, saints' days and holy days, and the Golden Numbers, together with the months and days of the Gregorian calendar. Engraved ornamental decoration to surround. 36-1/2 by 27 inches. Some age-darkening and toning, slight craquelure of varnish in some areas, expected age wear, overall very fine condition. Turin, 1745.
Perpetual calendars are valid for many years, and often were designed to allow the calculation of the day of the week for a given date in the future. This particular calendar allows for the determination not only of days of the week but more advanced systems from the ecclesiastical calendar. The Dominical Letter is a method used to determine the day of the week for particular dates, assigning a letter to each year based on when the first Sunday of January falls. The Epact is the age of the ecclesiastical moon on January 1. The Golden Number refers to the 19-year Metonic cycle by which the phases of the moon recur on the same dates, and where in the 19-year cycle the current year falls is the Golden Number. The Epact and Golden Number systems are primarily used to calculate the calendar date of Easter Sunday, which varies from year to year because of the difference in the solar year (365-366 days) and the lunar year (354-355 days). Overall a fascinating example of an antique perpetual calendar. Provenance: descended through the Rossi di Montelera family (of Martini & Rossi fame). Book ID: 48791