protected function formatDateCellValue($node)
    {
        // The XML node looks like this:
        // <table:table-cell calcext:value-type="date" office:date-value="2016-05-19T16:39:00" office:value-type="date">
        //   <text:p>05/19/16 04:39 PM</text:p>
        // </table:table-cell>

        if ($this->shouldFormatDates) {
            // The date is already formatted in the "p" tag
            $nodeWithValueAlreadyFormatted = $node->getElementsByTagName(self::XML_NODE_P)->item(0);
            return $nodeWithValueAlreadyFormatted->nodeValue;
        } else {
            // otherwise, get it from the "date-value" attribute
            try {
                $nodeValue = $node->getAttribute(self::XML_ATTRIBUTE_DATE_VALUE);
                return new \DateTime($nodeValue);
            } catch (\Exception $e) {
                return null;
            }
        }
    }