XML/JSON export must return dates with milliseconds

Today an export returns date values with milliseconds truncated to only 2 digits of precision, instead of the full 3 that is stored.
The XML export has:

<dc:modified><![CDATA[2017-02-08T22:24:59.36Z]]></dc:modified>

The JSON export has:

"lastModified": "2017-02-08T22:24:59.36Z"

But we should actually have: 2017-02-08T22:24:59.362Z