From: Svensson, Lars
> Are there any plans to register datatypes for EDTF datestrings in order to
> transport those in e. g. RDF (à la "2001-34"^^edtf:seasonCode)?

Glad you mentioned that. 
We registered this several years ago.  
(or in rdf: )

We haven't publicized it, but you're free to use it, e.g.   "2001-34"^^edtf:EDTF"
where  edtf:  is the prefix for 

There is a slight complication.  itself is a datatype scheme, meaning it is a group of datatypes, four of them, one for edtf in general and one for each level.   I am going to try to get this changed.  I don't think there needs to be more than one datatype (edtf general) and therefore no scheme. 

If we make this change,  you would instead say:     2001-34"^^someprefix:EDTF
Where the prefix is for   (I don't know at this time what the recommended prefix will be, because we don't define any other active datatypes.)
I'll keep you posted on this.