Remind is a full-featured calendar/reminder program featuring sophisticated date calculation, moon phases, sunrise/sunset, Hebrew calendar, alarms, PostScript output, an X front-end, multilingual messages, and proper handling of holidays. It also includes scripts for making a nice WWW calendar server.
When is an extremely simple personal calendar program, aimed at the Unix geek who wants something minimalistic. It can keep track of things you need to do on particular dates. It's a very short and simple program, so you can easily tinker with it yourself. It doesn't depend on any libraries, so it's easy to install. You should be able to install it on any system where Perl is available, even if you don't have privileges for installing libraries. Its file format is a simple text file, which you can edit in your favorite editor.
Web Calendar is a powerful group calendaring and scheduling system. It is a Web based application that makes it easy to publish and manage calendar events on the internet. It includes an impressive set of features, including an easy to use interface, rich functionality, and sophisticated scheduling. It is a CGI application. It runs under your Web server, so to use it, all you need is a browser. There is no proprietary software that needs to be installed on the client side. Web Calendar runs under Unix and Windows.
Wcal is a Web-based calendar and planner especially suitable for multi-user setups in an intranet. It features the ability for several users to have their own or shared calendars, read-only views, Weekly and monthly repeating events. It uses the Web server's access control methods, and allows a separate access control definition for each user.
Calcium provides interactive calendars you can use through your browser. Features include: dynamic calendar merging (events from one calendar can be included in another), multiple views and formats, repeating events, email support, extensive color and font customization, support for full HTML in the event text and calendar headers and footers, popup text associated with any event, searching and filtering, multi-language support, a flexible security model, and more. Calcium is very easy to use, and fully supported by an established company. It runs anywhere that supports Perl CGIs; no non-standard Perl modules are necessary. Full 2-way synchronization with Palm Pilots or MS Outlook is available; iCalendar "subscriptions" are supported too.
HERMES is a Web application framework designed to help provide a rapid application development framework for business tools with an initial focus of CRM (application included). It provides an integrated and flexible approach to business tools, and allows for database abstraction, library models, user rights management, and other critical areas.
WebCal is a free browser-based calendar program to help you keep track of your appointments, meetings, birthdays, etc. It's simple, yet has powerful scheduling features, email reminders, and a user-friendly interface, and being Web-based makes it ideal for use by groups of people.