Inqlude provides a comprehensive listing of all existing libraries for developers of applications using the Qt toolkit. Inqlude is run by the community and open for contributions.
The KDE calendar access library
KCalendarCore supports the standard formats iCalendar and vCalendar and the group scheduling standard iTIP.
A calendar contains information like incidences (events, to-dos, journals), alarms, time zones, and other useful information. This API provides access to that calendar information via well known calendar formats iCalendar (or iCal) and the older vCalendar.