Calendrical Calculations [Paperback]

Nachum Dershowitz (Author), Edward M. Reingold (Author)

Book Description

ISBN-10: 0521702380 | ISBN-13: 978-0521702386 | Publication Date: December 10, 2007 | Edition: 3

A valuable resource for working programmers, as well as a fount of useful algorithmic tools for computer scientists, this new edition of the popular calendars book expands the treatment of the previous edition to new calendar variants: generic cyclical calendars and astronomical lunar calendars as well as the Korean, Vietnamese, Aztec, and Tibetan calendars. The authors frame the calendars of the world in a completely algorithmic form, allowing easy conversion among these calendars and the determination of secular and religious holidays. LISP code for all the algorithms are available on the Web.

Editorial Reviews

Review

"Because years, months, and days don't mesh simply, calendar making has been a challenge throughout history. Dershowitz and Reingold's compendium, here in its third edition, has already established itself as the definitive reference on calendrical structures. Their manual displays conversions between all the major calendar systems as well as between many fascinating schemes from bygone civilizations." Owen Gingerich, Harvard-Smithsonian Center for Astrophysics

"One of the most fascinating books I've read all year. Takes chronology into the computer age with impressive erudition and elan. Just finding out what the calendar rules are is usually close to impossible; Calendrical Calculations tell you how to use them too. A must for everyone who worries about days, months, years - and why they never quite fit." Ian Stewart

"A good, comprehensive documentation of software for calculating dates on very many calendars." P. Kenneth Seidlmann, Director of Astronomy, U.S. Naval Observatory

"One of those rare books that is both an authoritative reference source and a fun read." Danny Hillis

"The book is a definitive account of the world's major calendars and how to use them. It will be of interest not only to mathematicians, but also to historians and laymen. The authors are to be congratulated on a splendid research job." Martin Gardner

"This book must surely become the standard work on calendar conversions. No historian, chronologist, or recreational mathematician should be without it." E.G. Richards, Nature

Book Description

This new edition of the popular calendars book expands the algorithmic treatment of the previous edition to new calendar variants: generic cyclical calendars and astronomical lunar calendars as well as the Korean, Vietnamese, Aztec, and Tibetan calendars. LISP code for all the algorithms are available on the Web.

See all Editorial Reviews

Product Details

• Paperback: 512 pages
• Publisher: Cambridge University Press; 3 edition (December 10, 2007)
• Language: English
• ISBN-10: 0521702380
• ISBN-13: 978-0521702386
• Product Dimensions: 9.2 x 6.6 x 0.9 inches
• Shipping Weight: 1.4 pounds (View shipping rates and policies)
• Average Customer Review: 4.4 out of 5 stars  See all reviews (9 customer reviews)
• Amazon Best Sellers Rank: #631,383 in Books (See Top 100 in Books)

More About the Author

Discover books, learn about writers, read author blogs, and more.

Customer Reviews

Most Helpful Customer Reviews

18 of 20 people found the following review helpful:

5.0 out of 5 stars highly readable and reliable description of many calendars, April 28, 1999

By A Customer

This review is from: Calendrical Calculations (Paperback)

The book explains the structure of 14 calendars, and gives easily comprehensible formulae for the conversion of a date in any of these calendars into a day count, and back to the calendar date. It also includes many holidays for these calendars.

Rather than on the history of calendars or their cultural background, the focus is on a lucid, correct, and complete exposition of their functional principles. Extensive bibliographic references are given to the primary sources for each calendar.

A highlight is the complete specification of several calendars depending on fairly precise timings of astronomical phenomena (Chinese calendar and some Hindu religious calendars).

To make it self-contained, the book explains the necessary mathematical and astronomical background. The astronomical models are taken from the classic 1991 book "Astronomical Algorithms" by Jean Meeus.

I especially like the presentation of the calendrical formulae in an essentially non-algorithmic manner, using normal mathematical notation. This makes it easy to further analyze these formulae.

For instance, if one wants to know how good an approximation to the spring equinox is March 21 in the Gregorian calendar, one finds from the formula on page 36 in the book that midnight of March 21 in Gregorian year Y is exactly

Y·365.2425 - (Y mod 4)·97/400 + (floor(Y/4) mod 25)·3/100 - (floor(Y/100) mod 4)/4

days after midnight of March 21 in Gregorian year 0, which ranges from Y·365.2425 - 1.4775 up to Y·365.2425 + 0.72. Thus, even assuming the Gregorian approximation of 365.2425 days to the tropical year, spring equinoxes are distributed over at least three dates in March in the Gregorian calendar.

Such reasonings would be very difficult if the book specified the calendars only in terms of programming language code.

The formulae are designed so that it is easy to incorporate them into code written in the programming language of your choice. This use is further supported by a set of test dates in an appendix. Another appendix lists an example implementation of all the formulae, in the programming language Common Lisp. This code (intended for personal use) can also be downloaded from the internet.

But this book is much more than a collection of programming recipes for many calendars -- it makes you understand the structure of those calendars. Ambitious readers can even find the data and the methods to construct their own calendrical formulae.

What would I like to be changed in the book? Not much. Some of the calendrical formulae could be further simplified, the astronomical terminology could be modernized in places, and perhaps some additional historical information could be added. And, of course, even more calendars! For instance, some of the proposed reformed calendars, a more widespread version of the Persian calendar, or an historic Japanese calendar.

This book is a must for everybody wanting reliable and highly readable information on the functional principles of the world's calendars.

Michael Deckers

52 of 65 people found the following review helpful:

1.0 out of 5 stars Potentially good book rendered totally useless by license., April 1, 1999

By A Customer

This review is from: Calendrical Calculations (Paperback)

If it were possible to give this book a ZERO rating, I would have done so. Right on page xxi, the authors purport to license their "Functions (code, formulas, and calendar data)" subject to both copyright and unspecified pending PATENT claims, and to restrict the use of such "Functions" to "strictly personal use." This is a book review, not a tutorial on patent law, so I don't even want to comment on the dubious validity of a PATENT claim covering purely mathematical functions. The authors are entitled to copyright protection on their actual source code examples, but asserting PATENT claims over mathematical functions is fundamentally abusive to the reader. As a result, if you have any practical goal for the information in this book and are considering it for other than mere personal amusement value, buy some other book instead. The license is particularly egregious since, on page xix, the authors explicitly acknowledge that all but two of the historical calendars are represented in GNU Emacs from the Free Software Foundation, proponent of the "copyleft" GNU General Public License!

27 of 33 people found the following review helpful:

5.0 out of 5 stars An excellent book with a mean spirited license, January 3, 2000

By 

J. Harris "virtualtraveler" (San Francisco, CA USA) - See all my reviews
(REAL NAME)   

This review is from: Calendrical Calculations (Paperback)

An excellent book on the history and workings of various calendars. But dont use the source code! The licensing agreement is a trap. Use the code in GNU Emacs from the Free Software Foundation distributed under the General Public License. It does everything the authors code does (except for two obscure calendars) and it's free and always will be.