If you're looking at how to test whether or not a date is valid, use this JavaScript function below to test your dates. Any recommendations, improvements etc are welcome.

function isDate(year, month, day) {
   month = month - 1; // javascript month range 0 - 11
   var tempDate = new Date(year,month,day);
   if ( (year == tempDate.getFullYear()) &&
    (month == tempDate.getMonth()) &&
    (day == tempDate.getDate()) ) {
      return true;
   } else {
      return false;
   }
}

revision 1

Date.isValid = function(year, month, day) {
   month -= 1; // javascript month range 0 - 11
   var tempDate = new Date(year,month,day);
   if ( (year == tempDate.getFullYear()) &&
    (month == tempDate.getMonth()) &&
    (day == tempDate.getDate()) ) {
      return true;
   } else {
      return false;
   }
}

revision 2