rem: return this.appendRecurrenceItem(d); 
add: this.removeExceptionFor(d.date);  this.appendRecurrenceItem(d); 
context:     removeOccurrenceAt: function (aRecurrenceId) {        if (!this.mBaseItem)            throw Components.results.NS_ERROR_NOT_INITIALIZED;        if (this.mImmutable)            throw Components.results.NS_ERROR_OBJECT_IS_IMMUTABLE;        var d = Components.classes["@mozilla.org/calendar/recurrence-date;1"].createInstance(Components.interfaces.calIRecurrenceDate);        d.isNegative = true;        d.date = aRecurrenceId.clone();        return this.appendRecurrenceItem(d);    },
meta: 9421	/local1/tlutelli/issta_data/temp/all_js/javascript/2006_temp/2006/9421/10ea06cc96fb0d01a787ec41c50247320258c1d4/calRecurrenceInfo.js/buggy/calendar/base/src/calRecurrenceInfo.js