Issue #3214669: Fix date format in sample content
www-data@ad910190dfec:/app$ drush -y en sector_events
In DateTimeNormalizer.php line 117:
The specified date "2016-09-01T14:00:00" is not in an accepted format: "Y-m-d\TH:i:sP" (RFC 3339), "Y-m-d\TH:i:sO" (ISO 8601).
Closes #3214669