rem: event.calendar.modifyItem(event, aOccurrence, null); 
add: event.calendar.modifyItem(event, aOccurrence.parentItem, null); 
context:     deleteOccurrence: function (aOccurrence) {        if (aOccurrence.parentItem != aOccurrence) {            var event = aOccurrence.parentItem.clone();            event.recurrenceInfo.removeOccurrenceAt(aOccurrence.recurrenceId);            event.calendar.modifyItem(event, aOccurrence, null);        } else {            aOccurrence.calendar.deleteItem(aOccurrence, null);        }    }
meta: 10234	/local1/tlutelli/issta_data/temp/all_js/javascript/2006_temp/2006/10234/502fcf12db44bbc249fff2508a280af215db63ce/calendar-management.js/clean/calendar/lightning/content/calendar-management.js