title: firebase: date object methods return the wrong values
body: <p>I'm trying to decompose a date I got from Firestore. Here's the source code:</p>
  
  <pre><code>exports.computeStatistics = functions.https.onRequest((request, response) =&gt; {
      let validatedViolations = [];
      const getValidatedViolations = db.collection("violations").where("validated", "==", true).get().then(snapshot =&gt; {
          return snapshot.forEach(doc =&gt; {
              validatedViolations.push({
                  type: doc.data().type,
                  date: doc.data().date.toDate()
              });
          })
      });
  
      getValidatedViolations.then(snapshot =&gt;{
          return console.log(validatedViolations[0].date.getMonth(),validatedViolations[0].date.getDay());
      })
  
  });
  </code></pre>
  
  <p>the date value is the following:</p>
  
  <pre><code>2019-11-14T00:00:00.000Z
  </code></pre>
  
  <p>but the outputs of the <code>getMonth()</code> and <code>getDay()</code> methods are respectively <code>10, 4</code> which are wrong.
  What's the problem?
  Thank you. </p>