Plans lets you put calendars on the web.

Sharp-looking
    - Plans is the nicest-looking web calendar.
    - Plans has several downloadable themes available.
    - CSS-based layout makes it easy to match the colors & fonts with
      your website.
Open Source
    - Plans is licensed under the GPL. You can freely modify the code
      for your needs. Many organizations have done so.
Multiple Calendars
    - One installation of plans can support many calendars.
    - Calendars can share information with each other.
    - Each calendar is managed independently (unique password, custom
      options, custom look & feel).
    - Multiple calendars running on the same installation of plans
      can be "embedded" in completely different websites.
Extendable
    - Plans' architecture allows add-ons and standalone programs
      to re-use its framework.
International Support
    - Plans supports multiple languages.
    - Weeks can start on days other than Sunday.
    - Plans supports arbitrary date formats (mm/dd/yy, dd/mm/yy, etc.)
Recurring Events
    - Plans uses a powerful and flexible recurring event model.
    - Template-based design
    - Plans uses HTML templates to allow easy customization of the
      look & feel.
    - Each calendar can have its own custom template, even located
      on a different server.
Browser-Based Management
    - Plans' interface is intuitive and easy to use.
    - Online help is built into Plans.
Database Support
    - Plans can store data in flat files or an SQL database.

WWW: http://www.planscalendar.com/
Author: Lloyd Dalton <daltonlp@gmail.com>