public static void deleteCalendar(String calendarID, UserRequest ureq) {
String calendarName = getImportedCalendarNameFromID(ureq.getIdentity(), calendarID);
// remove the entry from the database
PropertyManager pm = PropertyManager.getInstance();
Property p = pm.findUserProperty(ureq.getIdentity(), PROP_CATEGORY, calendarName);
pm.deleteProperty(p);
// delete the calendar file
CalendarManager calManager = CalendarManagerFactory.getInstance().getCalendarManager();
String importedCalendarID = getImportedCalendarID(ureq, calendarName);
String importedCalendarType = getImportedCalendarType();