> 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*. 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?
I can't help you directly, but you might want to pose this question to
emacs-devel@gnu.org.
IIRC, Ed Reingold wrote the calendar stuff for Emacs (in Emacs Lisp), so it is
likely that either this has already been done for Emacs (perhaps in a later
version than the one you're using) or it will be done. In any case, try asking
the Emacs developers about this (emacs-devel@gnu.org).