Anianus.Computus cum commento.1488.Lyon.indd

From the Tomash Library on the History of Computing 

Anianus, Computus cum commento, 1488, Lyons 

Computus cum commento. 

Year: 1488 

Place: Lyons 

Publisher: Jean du Pré 

Edition: 3rd 

Language: Latin 

Figures: Rubricated initials & paragraph marks 

Binding: Eighteenth-century grey-blue boards and label 

Pagination: ff. [40] 

Collation: a–e8 (a1 blank) 

Size: 195x142 mm 

Reference: 

Smith, David Eugene; Le comput manuel de Magister Anianus, Paris, Editions E. 

Droz, 1928, p. 106. 

Smith, David Eugene; Rara Arithmetica…, New York, Chelsea Publications, 1970, 

p. 31. 

Notes on the author and this work 

A computus is a work concerned with calculation of the church calendar and contains the rules for computing 

the date for Easter. In the “western” churches, Easter is the fi rst Sunday after the fi rst full moon after the spring 

equinox. Knowing the date for Easter for any given year, it is then possible to determine the dates for all the other 

movable Christian festivals. This calendar problem, essentially coordination of the solar with the lunar year, is 

of great consequence in the history of calculation in Europe, for it kept the study of mathematics alive during the 

so-called Dark Ages. 

Little is defi nitively known of Magister (master or teacher) Anianus; however, it is likely he was a French monk 

who lived in the second half of the thirteenth century at the Benedictine monastery of Aniane near Montpellier. 

His computus, which is well known in manuscript form, was fi rst printed in Paris in 1483, and this edition 

appeared fi ve years later. 

Most computus works tend to be prolix, obtuse and complex (see, for example, Schönborn; Computus, 1567, 

or Arnald of Villanova; Computus, 1501). In contrast, the Anianus computus is written in verse (including the 

fi rst printed Latin version of the verse Thirty days hath September…). The Anianus computations themselves are 

not algorithmic but are based on the use of the fi ngers and joints of the left hand as both a mnemonic aid and 

calculating device. The large number of incunable editions attests to the utility and popularity of this approachable 

work. 

This edition contains a short, fi ve page, commentary followed by the actual computus. It has three rather 

crudely drawn fi gures of the left hand as well as small circular devices and two pages of tables from which facts 

such as the golden number (the position in the lunar cycle for any given year) can be readily determined. 

For a succinct discussion of this method of computation, see Sachiko Kusukawa, A manual computer for 

reckoning time, in Claire Richter Sherman, Writing on hands. Memory and knowledge in early modern Europe. 

Seattle, 2000, pp. 28–34. For an earlier discussion of this work, see David Eugene Smith; Le comput manuel de 

Magister Anianus, 1928.

General notes on the condition of older books 



Books as old as this usually suffer from some problems just because of the wear they have been subjected to 

over the many years of their existence. One usually noticeable condition item is known as browning or foxing of 

the paper - usually brown or yellow areas due to the chemical action of a micro-organism on the paper. This can 

vary dramatically from page to page, often depending on such variables as the contents of the paper used, the 

composition of the ink used by the printer, and the dampness (or lack of) that the work has been exposed to over 

the years. Where these images were badly foxed, some slight manipulation of the intensity of the colors has been 

done to ease the reading of the foxed page. Any other notable condition problem will be commented upon near 

the image concerned. 

Use of these notes and images 

This fi le has been made available by the generosity of Erwin Tomash and the Tomash Library. It is free for use 

by any interested individual, providing that no commercial use is made of its contents and any non commercial 

use acknowledges the source. The notes and illustrations have been produced by Erwin Tomash and Michael R. 

Williams, both of whom beg forgiveness for any errors that they might have made. 

© 2009 by Erwin Tomash and Michael R. Williams. All rights reserved.

Front cover, spine and rear cover of the volume. 


Anianus, Computus cum commento, 1488, Lyons



Front paste down endpaper with the book plate of Sir George Shuckburgh and the Tomash Library label. 

George Shuckburgh (1751—1804) was an English mathematician and astronomer and was also the Member of 

Parliament for Warwickshire from 1780 to 1801. He was a Fellow of the Royal Society and won its highest award, 

the Copley Medal, in 1798.

Recto of the front free endpaper. 



Verso of the front free endpaper. 





Another front free endpaper (recto - the verso is identical).



This is the beginning of the commentary (usually referred to as the incipit) mentioned in the introductory notes.

Page 2 of the incipit. 












Verso of page 5 of the incipit. 





This is the fi rst page of the actual computus by Anianus.



As mentioned in the introductory notes, the computus uses the left hand as both a mnemonic device and to 

help with the calculations. This rather crude drawing of a left hand, palm up, is used to “set the scene” for this 

discussion.



Again a rather crude drawing of the left hand, this time palm down.











































This is the page with the famous “Thirty Days hath September...” In this version it reads: 

Annus solaris ex mensibus est duodenis (the solar year is divided into 12). 

Ja fe mar ap... (January, February, March , April ...). 

Juni aprilis september... (June, April, September and November) 

Dat trigita dies: reliquis supadditur vne (have 30 days: the rest are incireased by 1) 

The last three lines explain that February has an added day on leap years (known as bisextile years because the 

extra day was added as an extra “sixth” day before the fi rst of March).

























































































These tables are useful for calculating the date of Easter and other Christian festivals. 

The Golden Number (Aureus numerus) associates the phases of the moon with the calendar year (a cycle that 

repeats every 19 years so there are 19 golden numbers). The dominical letter (Littere domincales) is a letter from 

a to g which, for non-leap years, indicates which days of a year are Sundays. Assign the letter a to January 1, 

b to January 2, etc. then if the dominical letter for this year is b all days marked b will be a Sunday. For a full 

explanation of the calculation of Christian festivals (particularly Easter) consult any good encyclopedia.







This register lists the collation of the volume: a, b, c, d and e, each with 8 pages.

The printer’s mark of Jean du Pré. 







Rear paste down end paper.

Anianus.Computus cum commento.1488.Lyon.indd

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