X11 version by John Mackin, <john@cs.su.oz.AU>, based on a Suntools program
by John Walker, <kelvin@acad.uu.NET>.
 
This program is a clock that shows which portion of the Earth's surface is
illuminated by the Sun.  It is designed to be usually iconic, but can be
opened for a larger display with the time updated every second and both the
local timezone and UTC displayed.  The Suntools version had a menu that
allowed you to speed up time, show different dates, etc., but I have
never implemented any of that in the X version; there is some support
for it in the code, however.