function listMonthDays(month, element) {
   var d_end = 0;

   if (month.value == 1) {
      d_end = 31;
   } else if (month.value == 2) {
      d_end = 29;
   } else if (month.value == 3) {
      d_end = 31;
   } else if (month.value == 4) {
      d_end = 30;
   } else if (month.value == 5) {
      d_end = 31;
   } else if (month.value == 6) {
      d_end = 30;
   } else if (month.value == 7) {
      d_end = 31;
   } else if (month.value == 8) {
      d_end = 31;
   } else if (month.value == 9) {
      d_end = 30;
   } else if (month.value == 10) {
      d_end = 31;
   } else if (month.value == 11) {
      d_end = 30;
   } else if (month.value == 12) {
      d_end = 31;
   } else {
      d_end = 31;
   }

   removeAllOptions(element);

   element.options[0] = new Option('Day:', 0, 0, false);

   var i;
   for (i = 1; i <= d_end; i++) {
      element.options[i] = new Option(i, i, 0, false);
   }
}

function removeAllOptions(selectbox) {
   var i;
   for (i=selectbox.options.length-1;i>=0;i--) {
      selectbox.remove(i);
   }
}