The Automatic Calendar plug-in uses this to create feeds from the calendar data you give it.

But if you want to create an iCalendar/vCal format file using your data, use:

$feed->iCal($items);

If your events have an ending time as well as a beginning, specify it using “endtimestamp” or “enddatetime” just as you would for “timestamp” and “datetime”.

If an event starts at exactly midnight and has no endtimestamp or enddatetime, it is assumed to be an all-day event and is assigned a duration of 24 hours.