A XOOPS port of phpicalendar v 0.9.1

xCal is an ICS file renderer, and requires the use of an external calendar application to generate the ICS files. The README file lists several applications that can be used to generate the ICS file

From PHP iCalendar's README:
PHP iCalendar is a PHP-based iCal file viewer/parser to display iCals in a Web browser. Its based on v2.0 of the IETF spec. It displays iCal files in a nice logical, clean manner with day, week, month, and year navigation. It is available in 13 languages and includes support for printing, searching and RSS news feeds. If you need a Calendar application (for creating calendar files), please check the 'Supported Calendar Applications' section of the README.