from and until granularity

Regardles of the repository setting the from and until parameters must
handle day granularity.

see http://www.openarchives.org/OAI/openarchivesprotocol.html#SelectiveHarvesting

requests of the form request?verb=ListRecords&metadataPrefix=oai_dc&from=2014-09-08 produced `<error code="badArgument">Invalid date given in until parameter</error>`

The error message was fixed