Maybe this will help you to get rid of the six or seven numbers long date (most important part is the first part):
var sDate = "1212009";
if(sDate.length == 7){
sDate = sDate.substr(0,2) + "0" + sDate.substr(2);
}
else if(sDate.length == 6){
sDate = "0" + sDate.substr(0,1) + "0" + sDate.substr(1);
}
// This part can be done with Regular Expressions, as shown in other comments
var month = parseInt(sDate.substring(0,2));
var day = parseInt(sDate.substring(2,4));
var year = parseInt(sDate.substring(4));
alert(day + "/" + month + "/" year);
// Will alert 12/1/2009
However,
1232009 will always be 01/23/2009, not 12/03/2009
112009 changes to 1/1/2009
10102009 changes to 10/10/2009