title: SPARQL filter xsd:Date fails
body: <p>I have the following SPARQL query </p>
  
  <pre><code>PREFIX xsd: &lt;http://www.w3.org/2001/XMLSchema#&gt;
  
  SELECT DISTINCT ?d
  WHERE { GRAPH &lt;https:/my/triples&gt;{
          ?s &lt;http://my/ontology/v1.0#hasTimestamp&gt; ?d . 
          FILTER(?d &gt; "1945-01-01"^^xsd:date)
          }
  }
  </code></pre>
  
  <p>When i execute the above, it fails to filter correctly the results by date. Actually it gives me no results at all, and no errors.</p>
  
  <p>If i remove the date filter i get this response:</p>
  
  <blockquote>
  <pre><code>"bindings": [
    {
      "s": { "type": "uri" , "value": "seo:S2A_MSI_2019_11_28_09_33_31_T33SXB_t_dogliotti" } ,
      "d": { "datatype": "xsd:date" , "type": "typed-literal" , "value": "2019-11-28" }
    }
  </code></pre>
  </blockquote>
  
  <p>What could be wrong?</p>