The validation of some instances with BASE (Bielefelder Academic search engine) validator http://oval.base-search.net/ produced an ERROR for selective harvesting
" ERROR: No incremental harvesting (day granularity) of ListRecords: Harvest for reference date 2014-10-19 returned no records. Please make sure that the from and until parameters are evaluated."
OAI-PMH has from and until as optional arguments for ListIdentifiers and ListRecords in order to allow selective harvesting.
Allthough one might specify a finer granularity the basic YYYY-MM-DD must be supported see:
Trying to harvest a single day with from and until set to the same YYYY-MM-DD leads to no results allthough items with this date as last_modified are present an in the oai index.
Other combinations from only, until only from and until with at least 2 days seem to work.
On demo.dspace.org (5.1)
Gives an invalid date error whereas the full granular date works