The first version of Hebcal was developed by Danny Sadinoff in 1992,
and released on comp.lang.sources.misc.  There was a great deal of
feedback from the online community which helped it become a portable
program.

Hebcal is, at root, a port of the GNU Emacs Calendar lisp
code by Edward M. Reingold and Nachum Dershowitz.
http://emr.cs.iit.edu/~reingold/
http://www.math.tau.ac.il/~nachumd/


Michael Radwin has made significant contributions as a result of
maintaining hebcal.com.

Contributors include:
Ambrose C. Li
