<script type="text/javascript">
//
function IsDate(s) {
var re = /^(\d{4})(\/|-)(\d{1,2})\2(\d{1,2})$/
var m = re.exec(s);
if (m == null) return false;
var d = new Date(m[1],m[3]-1,m[4]);
return d.getFullYear()==m[1] && d.getMonth()==(m[3]-1) && d.getDate()==m[4];
}
alert(IsDate("2005-2-28"))
</script>