出来的日期不对

var mydate = new Date();
var iweeken= ["星期日","星期一","星期二","星期三","星期四","星期五","星期六"]
document.write("今天是阳历："+mydate.getFullYear() + "年" + mydate.getMonth() + "月" + mydate.getDay() + "日" + weekend[mydate.getDay()]+"<br  />");
//通过javascript的日期对象来得到当前的日期，并输出。