Book that goes over mathematics of calendar computations?

Question

What is a good book that goes over mathematics of calendar computations (e.g., calendar systems, date of Easter, etc.)?

Answer 1

Edward M. Reingold of the Illinois Institute of Technology and Nachum Dershowitz of Tel-Aviv University wrote an article titled "Calendrical Calculations" in Software--Practice and Experience, Vol. 20(9), September 1990, when the authors were both at the University of Illinois Champaign-Urbana. This paper, which is available for download on-line, covered the Gregorian, ISO, Julian, Islamic, and Hebrew calendars, including various holidays, in particular Easter. There was a second paper, "Calendrical Calculations, II: Three Historical Calendars," in 1993.

In 1997, Reingold and Dershowitz expanded the topic to an entire book, again titled Calendrical Calculations. The book is now in its fourth edition, which adds numerous other secular and religious calendars and astronomical calculations.

I'm fairly certain that the calculation of Easter (among other holidays) is still included in the book, as the intention seems to have been to add information rather than to remove it.

The 1990 paper included LISP code for the calculations. The code is still on line. The book supposedly also comes with access to code, with full documentation of the code in an appendix of the book.

I have not read the book, but I did read the two papers shortly after they were published, and I found them very useful. I have every reason to expect that the book is just as clear and straightforward (at least as straightforward as one could conceivably get with a topic that has so much inherent complexity).