Incrementare una data

<script>
    <!--
 function Calcola() {
 
   
  
var campodata = document.getElementById("MyData").value; // o altro sistema per leggere una var
var separ = campodata.split(/[\/\.\-]/);
var giorno = new Date(separ[2], parseInt(separ[1],10)-1, separ[0]);
giorno.setDate(giorno.getDate()+1); // giorno sucessivo
var res =  giorno.toLocaleString();
res = res.replace(", 00:00:00","")
document.getElementById("MyData").value = res  //giorno.toLocaleString()

}//-->

</script>

</HEAD>
<BODY>

<div id="navbar"> 
       <table width="50%" align="Center"> 
           <tr>
               <td witdh="50%" align="center">
 <a href="default.asp"> <font size="+2": style="text-shadow": color="#FFFFFF":> Home </font></a>      
</td> 
  <td >
<form id="mio" action="CalendarioNew.asp" style="alignment-adjust: central" method="get" >
  <label for="fname">Inserisci Data:</label> 
  <input type="text" id="MyData" name="MyData" value="<%=stringa2%>" ondblclick="Calcola()" style="text-align: center"> 
  <input type="submit" value="Cerca">   <div class="tooltip"><font color="#FFFFFF">(*)</font><span class="tooltiptext"><%=Percorso%> </span></div>  
</form> 
   </td>
  </tr>
  </table>      
  </div>

<script>


</script>

</HEAD>
<BODY>

<div id="navbar">
<table width="50%" align="Center">
<tr>
<td witdh="50%" align="center">
<a href="default.asp"> <font size="+2": style="text-shadow": color="#FFFFFF":> Home </font></a>
</td>
<td >
<form id="mio" action="CalendarioNew.asp" style="alignment-adjust: central" method="get" >
<label for="fname">Inserisci Data:</label>
<input type="text" id="MyData" name="MyData" value="<%=stringa2%>" ondblclick="Calcola()" style="text-align: center">
<input type="submit" value="Cerca"> <div class="tooltip"><font color="#FFFFFF">(*)</font><span class="tooltiptext"><%=Percorso%> </span></div>
</form>
</td>
</tr>
</table>
</div>