Tip: ExtCalendar is a powerful multi-user web-based calendar application. Some of ExtCalandar's features include multi-languages, themes, recurrent events, categories, users and groups management, environment and general settings, template configuration and product updates. ExtCalendar is an open-source calendar application, with an integrated event management system. That's right, free for both commercial and personal use. In addition to this you are also allowed to modify ExtCalendar to make it do exactly what you want. Below are the best Extcalendar web hosting companies on the internet.