js 计算年差

var date1 = new Date("1996/06/21");
var date2 = new Date("2011/11/26");
var fm=date1.getMonth();
var sm=date2.getMonth();
var dd1=(sm-fm)*30+(date2.getDate()-date1.getDate());
var year = date2.getFullYear() - date1.getFullYear()+dd1/360;