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. Version : 1.2.7
Booked (formerly phpScheduleIt) is a simple but powerful reserve-anything scheduler. With flexible layouts, custom rules, a powerful administrative backend, and an unbelievably simple user experience, Booked can fit almost any need. From conference rooms to lab equipment to airplanes - it's Booked. Version : 2.5.12
ExtCalendar is an open-source calendar application, with an integrated event managemt system.
ExtCalendar is a powerful multi-user web-based calendar application. Features include Multi-Languages, Themes, Recurrent Events, Categories, Users and Groups management, Environment and General Settings, Template Configuration, Product Updates. Version : 2.0