query: PREFIX wikibase: <http://wikiba.se/ontology#>
  PREFIX p: <http://www.wikidata.org/prop/direct/>
  PREFIX xsd: <http://www.w3.org/2001/XMLSchema#>
  
  SELECT ?item ?date
  WHERE {
      ?item p:P569 ?date .
      FILTER REGEX(str(?date), "-02-30T")
  }
  LIMIT 10