Javascript getUTCDate returns "31" as day when picking 2013/04/01?

Question

In javascript, by using the method getUTCDate() a error came.

with a datepicker a chose a the date 2013/04/01, but the getUTCDate() returns 31 for the same month and year. By using the method getDate() the return number is 1. seems a bug to me but...

why does this happen?

My UTC+00 -- Portugal

<script>
   function myFunction() {
     var dataToData = new Date();
     dataToData = $("#datepicker").datepicker("getDate"); //ui-jquery datepicker

     var yearDpick = "";
     var monthDpick = "";
     var dayDpick = "";

     var monthaux = dataToData.getMonth() + 1;
     var dayaux2 = dataToData.getUTCDate();
     var dayaux = dataToData.getDate();
     yearDpick += dataToData.getFullYear().toString();

      if (monthaux > 9) {
           monthDpick += monthaux.toString();
           } else monthDpick += "0" + monthaux.toString();

       if (dayaux > 9) {
          dayDpick += dayaux.toString();
          } else dayDpick += "0" + dayaux.toString();



       alert(dayaux2.toString());

       alert(yearDpick+monthDpick+dayDpick);
   }
 </script>

Answer 1

Because you're not living in UTC. You're probably living in UTC+xx. If you set a date with setDate, don't use getUTCDate later. Keep in mind that new Date() will use your local time instead of UTC if you use a string as argument.