rem: this.mCalendar.modifyItem(this.mOldItem, null); 
add: this.mCalendar.modifyItem(this.mOldItem, this.mItem, null); 
context:     undoTransaction: function () {        switch (this.mAction) {            case 'add':                this.mCalendar.deleteItem(this.mItem, null);                break;            case 'modify':                this.mCalendar.modifyItem(this.mOldItem, null);                break;            case 'delete':                this.mCalendar.addItem(this.mItem, null);                break;            case 'move':                this.mOldCalendar.addItem(this.mOldItem, this.mListener);                this.mCalendar.deleteItem(this.mItem, this.mListener);                break;        }    },
meta: 10234	/local1/tlutelli/issta_data/temp/all_js/javascript/2006_temp/2006/10234/f0c77cac48e7ce31af529637a1b48c03f4314901/calendar.js/buggy/calendar/resources/content/calendar.js