README.txt 
  CalendarX 0.5.3(dev)  March 26 2005
  (last modified for CalendarX 0.5.3)
by +lupa+ (lupaz on sf.net, lupa at zurven dot com)
Released under the GPL (see LICENSE.txt)

Release Summary: 0.5.3 is a bugfix release.  Fixed helpcx.pt so that it works 
  properly with 0.5 branch.  Fixed the +link bug for datestrings in the URL 
  query that were not properly quoted for use in query strings.  Fixed 
  portlet_calendarxp bug that displayed wrong events in overlapping dates 
  (such as both March 1 and April 1 in the same view).  Fixed calendarPrint 
  problem where the print version was NOT removing subjectlinks.  Added new 
  property to cx_props_addeventlink to turn on/off the +links, and made mods 
  to utilize this property. 
Attempted but did NOT fix the problem with addNewEvent links not using 
  portal_factory when Events are selected there: current status is that 
  portal_factory is bypassed, but with a documented one-line change in 
  cxCreateEvent.py, you can allow portal_factory to be used even though the 
  proper date, time, Title and Description parameters will NOT be passed 
  in to the temporary event.


CalendarX is a customizable, open source metacalendar application written 
for the Plone content management system on top of Zope and Python.

Read the INSTALL.txt document for details, but in essence, put the CalendarX
folder in your /Products folder, restart Zope, use the portal_quickinstaller
to add CalendarX.  Then add a CalendarX instance through Plone using the 
normal methods.  

CUSTOMIZATION:  Customize property sheets or other objects found in the 
/portal_skins/CalendarX folder.  Use ZMI to move these into your CalendarX 
instances (from the /custom folder) to restrict the customization to that 
one CalendarX instance.  This allows creation of multiple CalendarX instances
and also subcalendars (use ZMI to add new subcalendars within a main calendar
instance).

There is fairly extensive new documentation in the /docs folder.  Please 
read these for help in figuring out all the configuration.  CalendarX has 
lots of options, and reading the docs helps a lot.  In particular, there are
now many options for configuring who can see what types of events on each
calendar instance on your site.
 

Read more at these sites:

http://calendarx.sourceforge.net
http://sourceforge.net/projects/calendarx/
http://calendarx.org
http://crashtest.calendarx.org