WebCalendar is an open source calendar application. WebCalendar was initially released in 2000 and today has been downloaded more than 1.2 million times. WebCalendar is a 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.

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.

Features:

• Multiple users and user management functionality.
• View calendars by day, week, month or year.
• View another user's calendar.
• View one or more users' calendar via layers on top of your own calendar.
• Repeating events including support for overriding or deleting (exceptions).
• Configurable custom event fields.
• User-configurable preferences for colors, 12/24 time format, Sun/Mon week start.
• Checks for scheduling conflicts.
• Email reminders for upcoming events and notifications for new/updated/deleted events.
• Import and Export events to iCalendar, vCalendar or Palm.
• Optional general access (no login required) to allow calendar to be viewed by people without a login (useful for event calendars).
• Users can make their calendar available publicly to anyone with an iCalendar-compliant calendar program (such as Apple's iCal, Mozilla Calendar or Sunbird).
• Publishing of free/busy schedules (part of the iCalendar standard).
• RSS support that puts a user's calendar into RSS.
• Subscribe to "remote" calendars (hosted elsewhere on the Internet) in either iCalendar or hCalendar formats.