The files dates.cpp, dates.h, watdefs.h are from 
http://www.projectpluto.com/source.htm#date_cpp
and are copyright (c) Project Pluto.

The authors write: 
"Copyright restrictions:  All this code is free for use in non-commercial applications. If you wish to use any of it in a commercial application, please let me know; I'm not averse to a little bartering in such cases. "


The files convdates.c and convdates.R are by Thomas Lumley and are
placed in the public domain.