title: Javascript Add Date Problem
body: <p>I've this snippet:</p>
  
  <pre><code>var d1 = parseInt( document.getElementById('day1').value );
  var m1 = parseInt( document.getElementById('month1').value );
  var y1 = parseInt( document.getElementById('year1').value );
  
  var dt = new Date();
  dt.setYear(y1);
  dt.setMonth(m1);
  dt.setDate(d1 + 1);
  
  document.getElementById('day2').value = dt.getDate();
  document.getElementById('month2').value = dt.getMonth();
  document.getElementById('year2').value = dt.getYear();
  </code></pre>
  
  <p>My goal is, to automatically init value of date2 by adding 1 day from date1.
  However, when I fill :</p>
  
  <pre><code> day1 = 32
   month1 = 1
   year1 = 2009
  </code></pre>
  
  <p>I got :</p>
  
  <pre><code> day1 = 5
   month1 = 2
   year1 = 2009
  </code></pre>
  
  <p>I don't know what is going on. Do you guys know the solutions?</p>