query: SELECT ?item ?itemLabel ?value ?valueLabel ?start ?end
  {
    ?item p:P485 ?stmt .
    ?stmt ps:P485 ?value .
    OPTIONAL {
      ?stmt pqv:P580/wikibase:timeValue ?start .
    }
    OPTIONAL {
      ?stmt pqv:P582/wikibase:timeValue ?end .
    }
    FILTER(BOUND(?start) || BOUND(?end))
    SERVICE wikibase:label { bd:serviceParam wikibase:language "en,en"  }
  }
  LIMIT 1000