The Calendar Base extension facilitates Backend data entry, Frontend data entry, as well as parsing of static iCal feeds and subscriptions to external iCal content. Frontend Registration and logins can limit which appointments are displayed, thus allowing the use of “multiple calendars” for personal appointments, etc. In addition to standard calendar data, extensions such as tt_news can be configured for calendar display. Data from each of these source is combined into a single calendar, offering multiple views such as list, day, week, and month. In addition to the standard HTML views, iCal feeds and RSS feeds are produced by the Calendar Base.