Bedework is a mature, open-source enterprise calendar system that
supports public, personal, and group calendaring. It has a
platform-independent, modular and extensible design and Its strict
adherence to calendaring standards allows it to work with other
calendaring systems and clients. Bedework is used by colleges,
universities, library systems, and companies all over the world.

The latest release is 3.10, which features a revamped public client skin that works on virtually all display sizes. Also new: integrated web page cache and improved feed builder.