extjs 日期不显示

Ext.onReady(function(){
//初始化全局 QuickTips 实例  使得tip提示可用
Ext.QuickTips.init();
//别名
var xg=Ext.grid;

//创建一个ArrayReader
var reader=new Ext.data.ArrayReader({},[
{name:"name",type:"string"},
{name:"age",type:"int"},
{name:"empno",type:"int"},
{name:"sex",type:"int"},
{name:"birthday",type:"date",dateFormat:"n/j h:ia"},
{name:"salary",type:"float"},
{name:"deptno",type:"int"},
{name:"desc",type:"string"}
]);

//创建一个RowExpander,行展开的时候的样式
var expander=new Ext.ux.grid.RowExpander({
tpl:new Ext.Template(
'<p><b>姓名:</b>{name}</p><br/>',
'<p><b>描述信息:</b>{desc}</p>'
)
});

//性别的ernderer
function sexCls(val){
return val==0? "male" : "female";
}

//创建一个grid
var grid1=new xg.GridPanel({
store:new Ext.data.Store({
reader:reader,
data:xg.dummyData//数据模型
}),
cm:new xg.ColumnModel({
defaults:{
width:20,
sortable:true
},
columns:[
expander,
{header:"姓名",dataIndex:"name"},
{header:"年龄",dataIndex:"age"},
{id:"empno",header:"编号",width:40,dataIndex:"empno"},
{header:"性别",dataIndex:"sex",renderer:sexCls},
{header:"生日",dataIndex:"birthday",renderer:Ext.util.Format.dateRenderer("Y-m-d"),dataIndex:"birtdhay"},
{header:"工资",dataIndex:"salary",dataIndex:"salary"},
{header:"部门编号",dataIndex:"deptno"}
]
}),
viewConfig:{//作用在grid's UI试图上的配置项对象， 任何Ext.grid.GridView可用的配置选项都可在这里指定。若view已指定则此项无效
forceFit:true
},
width:600,
height:300,
plugins:expander,
collapsible:true,//True表示为面板是可收缩的
animCollapse:false,//True 表示为面板闭合过程附有动画效果
title:"雇员的信息",
iconCls:"icon-grid", //为该面板设置图标的样式类。此方法会覆盖当前现有的图标
renderTo:document.body //提供到窗体的body上
});
});

//数据
Ext.grid.dummyData=[
["张三00",12,1001,1,"1990-05-20",3000,50],
["张三01",16,1002,0,"1990-05-21",3000,20],
["张三02",19,1003,1,"1990-05-22",3000,20],
["张三03",25,1004,1,"1990-05-23",3000,10],
["张三04",22,1005,1,"1990-05-24",3000,30],
["张三05",24,1006,1,"1990-05-25",3000,20],
["张三06",23,1007,0,"1990-05-26",3000,60],
["张三07",21,1008,0,"1990-05-27",3000,90],
["张三08",25,1009,0,"1990-05-28",3000,10],
["张三09",28,1010,1,"1990-05-29",6000,20],
["张三20",26,1011,0,"1990-05-20",2000,50],
["张三21",29,1012,0,"1990-06-20",8000,40],
["张三22",22,1013,1,"1990-01-20",3000,50],
["张三23",28,1014,0,"1990-02-20",3000,60],
["张三24",21,1015,1,"1990-08-20",3000,50]
];

// 添加描述信息
for(var i = 0; i < Ext.grid.dummyData.length; i++){
Ext.grid.dummyData[i].push('这个是一个简单的演示的信息,测试描述信息的.');
}