var s:String = "2012/03/05";
var dateParts:Array = s.split('/'); //['2012', '03', '05']
//take off the first element and add it back at the end
dateParts.push(dateParts.shift()); //['03', '05', '2012']
s = dateParts.join('/'); //'03/05/2012'
trace(s);