I think the reason for editing the files to use a parameter was to preserve the existing behavior if anyone wants it, but I wasn't really involved ...
iCalendar is a standard that defines an external representation for calendar data that is used by many calendar programs to exchange such data. In fact our calendar package uses that format to export data to MS Outlook. Gnome and KDE calendaring software also use iCalendar as does Lotus.
Another issue with the calendar package is that the object derivation is defined in such a way that attaching arbitrary objects to a calendar is a PITA. You have to kludge things heavily. It's been a long time since I've looked at this but there's an old thread around here somewhere in which I defined how I'd like to see it work and Ben had agreed at that time. But there was never time for OF to reimplement calendar that completely, unfortunately.
