Gets the selected date from all the scroll-wheels.
function _getDateFromScrollWheels() {
        var date = new Date(this._date);
        for (var i = 0; i < this.scrollWheels.length; i++) {
            var scrollWheel = this.scrollWheels[i];
            var component = scrollWheel.component;
            var item = scrollWheel.scrollController.getFirstVisibleItem();
            if (item && item.renderNode) {
                component.setComponent(date, component.getComponent(item.renderNode.date));
            }
        }
        return date;
    }