Data Type of datetime values of claimed publications missing

[matthiasluehr]

Description:

When importing a publication using the DOI claiming tool the publication's
DateTimeValue-Node is specified not as
http://www.w3.org/2001/XMLSchema#dateTime data type but rather as a plain
string:

http://vivoweb.org/ontology/core#dateTime "2015-01-01T00:00:00"

On the other hand, when crafting a publication manually using the UI it's
done properly:

http://vivoweb.org/ontology/core#dateTime "2015-01-01T00:00:00"^^http://www.w3.org/2001/XMLSchema#dateTime

Thus using SPARQL's aggregate date and time functions against the date time values generated by
the DOI claimer wont work.

To Reproduce
Claim a publication, edit the individual, find the DateTime Value and display raw statements of it:

The date is stored as a string.

Expected behavior
Should be stored as http://www.w3.org/2001/XMLSchema#dateTime data type.

Additional context
Check for bogus date time values:

SELECT ?uri ?litval ?year
WHERE {
  ?uri a <http://vivoweb.org/ontology/core#DateTimeValue> .
  ?uri <http://vivoweb.org/ontology/core#dateTime> ?litval .
  BIND (YEAR(?litval) AS ?year)
  FILTER (!bound(?year))
}