function setDays(form)
{
  year = parseInt(form.year.options[form.year.selectedIndex].value);
  month = form.month.selectedIndex;
  day = form.day.selectedIndex;
  form.day.options.length = 0;
  var days = new Array(31, ((year % 4 == 0 && year % 100 != 0) || year % 400 == 0 ? 29 : 28), 31, 30, 31, 30, 31, 31, 30, 31, 30, 31);
  for(i = 0; i < days[month]; i++)
  {
    form.day.options.length = form.day.options.length + 1;
    form.day.options[i].value = i + 1;
    form.day.options[i].text = i + 1;
  }
  form.day.selectedIndex = (day < form.day.options.length) ? day : form.day.options.length - 1;
}