KALENDARIUM GREGORIANUM PERPETUUM, ROME, 1582, NINETEENTH-CENTURY HALF CALF

8vo (163 x 94mm.), A-D8 E4, printed in red and black, woodcut papal arms on title-page within a cartouche, woodcut initials, nineteenth-century half calf over marbled boards, occasional light damp-staining, front flyleaf excised and title-page partly cut through along gutter

Antonius Vulpius, inscription at end; bought from Fiammetta Soave, Rome, 2000, bookseller's ticket on inside front cover

Tomash & Williams G83; Edit16 11280; Houzeau & Lancaster 13771 (listing 4 editions); Riccardi i, 654 (4to Basa edition); USTC 820844

Condition is described in the main body of the cataloguing, where appropriate
"In response to your inquiry, we are pleased to provide you with a general report of the condition of the property described above. Since we are not professional conservators or restorers, we urge you to consult with a restorer or conservator of your choice who will be better able to provide a detailed, professional report. Prospective buyers should inspect each lot to satisfy themselves as to condition and must understand that any statement made by Sotheby's is merely a subjective, qualified opinion. Prospective buyers should also refer to any Important Notices regarding this sale, which are printed in the Sale Catalogue.
NOTWITHSTANDING THIS REPORT OR ANY DISCUSSIONS CONCERNING A LOT, ALL LOTS ARE OFFERED AND SOLD AS IS" IN ACCORDANCE WITH THE CONDITIONS OF BUSINESS PRINTED IN THE SALE CATALOGUE."

This is one of many editions printed in 1582 containing the authorised calendar reform of Pope Gregory XIII. The reforms were proposed by Aloysius Lilius (died 1576), and given structure by Christoph Clavius. The two changes were to reduce the number of leap years (by 3 over a 400 year period) and to move the date forward by 10 days to allow for movement since the Council of Nicaea. In 1582, October 4 was immediately followed by October 15. An oddity of the Gregorian calendar is the omission of the year 0, as this was not considered to be a valid number in the sixteenth century.

Lilius's brother Antonius was granted the privilege for producing these calendars, but he could not cope with the demand so the privilege was revoked in September 1582. From the surviving copies it can be seen that production was farmed out to various printers in Rome and Venice, and in 1583 production moved further abroad.