Programs like iCal and Mozilla Calendar use the iCalendar format to store events. iCalendar is an open standard, see http://www.ietf.org/rfc/rfc2445.txt. This page is list of all resources on OS X to work with the format.

vCalendar is an older version of the iCalendar format.

* ** libical ** http://www.softwarestudio.org/libical/

libical is an open source C library that parses the iCalendar format. Mozilla Calendar uses libical and I believe so does iCal. libical includes libicalvcal, a library for converting between iCalendar and vCalendar formats.

* ** skyrix-xml ** http://www.opengroupware.org/en/devs/sope/skyrix_xml/

This is an LGPL library that provieds a Objective-C interface to parse XML. They also use libical to read iCalendar files.

* ** iCalendarParser ** http://www.oops.se/~malte/software.html

An iCalendar parser written in Objective-C. It’s at a very experimental stage right now and only handles the inital parsing of iCalendar content lines. It works in a fashion similar to a SAXParser.

* ** ics2vcs ** http://www.isi.edu/touch/tools/#software

Perl script converts iCalendar (.ics) to vCalendar (.vcs).

* ** CALCore **

Apple’s private framework for working with iCalendars.