<script type="text/javascript">
function CalculValabilitate() {
var tempdata = document.getElementById('data').value;
var vectordata = tempdata.split("/");
var zi = +vectordata[0];
var luna = +vectordata[1];
var an = +vectordata[2];
var ok=0;
if ((0<zi)&&(zi<32)&&(0<luna)&&(luna<13)&&(2000<an)&& (an<2100)) {ok=1;}
if (luna>9) {luna=luna-9; an=an+1;}
else {luna=luna+3;};
if (ok) {tempdata= zi +"/"+luna+"/"+an;}
else {tempdata="";}
document.getElementById("valabil").value=tempdata;
}
</script>
Data inceput: <input size=15 type='text' name='data' id='data' value='zz/ll/aaaa' onChange="CalculValabilitate()"> <br><br>
Valabil pana la: <input size=15 type='text' name='valabil1' id='valabil'>