The Calendar Base extension is a full-featured online calendar system that has been designed for expandability and interoperability with other extensions and programs, including popular calendar systems such as Yahoo! Calendar, Google Calendar, and Microsoft Outlook. In addition to these common calendar systems, Calendar Base is compatible with any other applications support the iCal standard data format.

The user interface is based up the PHP iCalendar project, available at phpicalendar.net. Many thanks to its developers for a great product to build upon.