title: Difference in JavaScript Date construction IE11
body: <p>We have an awkward problem with a couple of users in our organization.
  Let's say we can divide our user base in two populations:</p>
  
  <ol>
  <li>They are using some edition of Internet Explorer 11</li>
  <li>They are using some other edition of Internet Explorer 11. One difference we potentially see is that they are using the Dutch version of Internet Explorer 11.</li>
  </ol>
  
  <p>We see the following behavior when trying out on the JavaScript console:</p>
  
  <p>Testcase A</p>
  
  <pre><code>var x = new Date("1966-09-05")
  new Intl.DateTimeFormat('nl-NL').format(x)
  </code></pre>
  
  <ol>
  <li>Correct: "05-09-1966"</li>
  <li><p>Correct: "05-09-1966"</p>
  
  <p><code>x.toLocaleTimeString()</code></p></li>
  <li><p>Correct: "02:00:00"</p></li>
  <li>Correct: "02:00:00"</li>
  </ol>
  
  <p>Testcase B</p>
  
  <pre><code>var y = new Date(1966, 8, 5)
  new Intl.DateTimeFormat('nl-NL').format(y)
  </code></pre>
  
  <ol>
  <li>Correct: "05-09-1966"</li>
  <li>Incorrect: "04-09-1966"</li>
  </ol>
  
  <p><code>y.toLocaleTimeString()</code></p>
  
  <ol>
  <li>Correct: "00:00:00"</li>
  <li>Incorrect: "23:00:00"</li>
  </ol>
  
  <p>With the mark "Incorrect" we use Chrome, Firefox, Safari, etc. as a reference implementation, assuming they have implemented the specification correctly.</p>
  
  <p>It looks like that constructing a Date object with numeric parameters does not take daylight saving into account correctly. In one flow it is assuming "CEST" +02:00 Central-European Summer-Time and in the other flow it converts to "CET" +01:00 Central-European Time, substracting 1 hour of the clock, getting the date of the day before.</p>
  
  <p>Can anyone explain to us why Internet Explorer 11 has this behavior on these specific set of workstations? Is there any (Microsoft) documentation that explains this?</p>