if (document.getElementById('start_year_historic')!=null){
  document.getElementById('start_year_historic').disabled=true;
}
document.getElementById('start_year').disabled=true;
document.getElementById('start_day').disabled=true;
document.getElementById('start_month').disabled=true;
if (document.getElementById('end_year_historic')!=null){
  document.getElementById('end_year_historic').disabled=true;
}
document.getElementById('end_year').disabled=true;
document.getElementById('end_day').disabled=true;
document.getElementById('end_month').disabled=true;

var d;
d = document.getElementById('start_day').options;
      text = new Array(40);
      value = new Array(40);
      
 for (i = 0;i<= 30;i++)
 {
 text[i] = d[i].text;
 value[i] = d[i].value;
 }
 
 function dateName(prefix)
{

  var d;
  var y;
  var m;
  
  y = document.getElementById(prefix + '_year').options;
  y = y[document.getElementById(prefix + '_year').selectedIndex];
  y = y.value;
  d = document.getElementById(prefix + '_day').options;
  d = d[document.getElementById(prefix + '_day').selectedIndex];
  d = d.value;
  m = document.getElementById(prefix + '_month').options;
  m = m[document.getElementById(prefix + '_month').selectedIndex];
  m = m.value;
  
  return(y + '-' + m + '-' + d);

  
}
 

function dateErrorCheck(prefix){



var d;
var y;
var m;

  y = document.getElementById(prefix + '_year').options;
  y = y[document.getElementById(prefix + '_year').selectedIndex];
  y = y.value;

  m = document.getElementById(prefix + '_month').options;
  m = m[document.getElementById(prefix + '_month').selectedIndex];
  
  d = document.getElementById(prefix + '_day').options;
    d.length=31;
 
      
  if (m.value == "02"){
    if ( y % 4 != 0){
      d.length=28;      
    }
    else
    {
    d.length=29;
    d[28].text = text[28];
    d[28].value = value[28];

    }     
  }
  else{ 
   d[28].text = text[28];
    d[28].value = value[28];
    d[29].text = text[29];
    d[29].value = value[29];
  if (m.value=="04"){
    d.length=30;
  }
  else if (m.value=="06"){
    d.length=30;
  }
  else if (m.value=="09"){
   d.length=30;
  }
  else if (m.value=="11"){
    d.length=30;
  }
  else{
  d.length=31;
   for (i = 0;i<= 30;i++)
 {
 d[i].text =  text[i];
 d[i].value  =  value[i];
 }

 
  }
  }
}