哪里错了？
<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>获得年份 </title>
<script type="text/javascript">
var mydate=new Date();
document.write(mydate+"<br>")
var a=mydate.getFullYear();
document.write(a+"<br>");
var b=mydate.setFullYear(50);
document.write(b);
</script>
</head>
<body>
</body>
</html>
最后修改年份后输出的是-60574343280158，var b=mydate.setFullYear(50)这样写不是应该正确的？
