WebCalendar is a PHP-based calendar application that can be configured as a single-user calendar, a multi-user calendar for groups of users, or as an event calendar viewable by visitors. MySQL, PostgreSQL, Oracle, DB2, Interbase, MS SQL Server, or ODBC is required.

WebCalendar can be setup in a variety of ways, such as...

A schedule management system for a single person
A schedule management system for a group of people, allowing one or more assistants to manage the calendar of another user
An events schedule that anyone can view, allowing visitors to submit new events
A calendar server that can be viewed with iCalendar-compliant calendar applications like Mozilla Sunbird, Apple iCal or GNOME Evolution or RSS-enabled applications like Firefox, Thunderbird, RSSOwl, FeedDemon, or BlogExpress.

The license of this software is Free Trial Software, you can free download and get a free trial.