I would like to add a "module" to Emacs for converting from Gregorian dates
into traditional Indian/Hindu dates (Bikrama Samvat), and, perhaps more
importantly, for calculating Hindu holidays.

I found a very nice set of functions for doing so implemented in Common Lisp
in *Deshow, Nachum and Reingold, Edward M. 2008. _Calendrical Calculations_.
New York: Cambridge University Press, 3rd edn*. I was wondering if this
perhaps has already been implemented (given that Reingold developed the
original calendar calculations for Emacs).

If not: What is the best way of using this code in Emacs? I know that Emacs
Lisp is different from Common Lisp - and I also know that there is/are
package(s?) for using Common Lisp within Emacs.

What I don't know is:
(1) Can this code just be converted into Emacs Lisp? Or are there bits of it
which would require Common Lisp?

[Right now it doesn't work - I know that Emacs Lisp requires "defconst"
rather than "defconstant", but even changing that, I get a "condition-case:
Symbol's value as variable is void: 279457/1080000" error for:

 (defconst hindu-sidereal-year
  ;; TYPE rational
  ;; Mean length of Hindu sidereal year.
  (+ 365 279457/1080000))

And changing the definition to (+ 365 (/ 1080000 279457)) it seems just to
round.]

(2) Or else, if it is necessary, how to use Common Lisp packages in Emacs.

I have transcribed the code here:
http://www.jnanam.net/emacs/hindu-calendar.el [there are probably typos in
it yet].

I'm, obviously, not really a Lisp coder, but I am looking for some pointers
for how to get this code working within Emacs.

thanks,
  --Ben
-----------------------------------------------------------------------------------------------------
Benjamin Slade
Dept. of Linguistics
University of Illinois at Urbana-Champaign
[ http://www.jnanam.net/slade/ ]

Stæfcræft & Vyākaraṇa (lingblog) - http://staefcraeft.blogspot.com
The Babbage Files (techblog) - http://babbagefiles.blogspot.com

-----------------------------------------------------------------------------------------------------
  *प*रो ऽक्ष॑का*मा* हि *दे*वाः
    'The gods love the obscure.' (Śatapathabrāmaṇa 6.1.1.2)