combobox怎么处理日期格式？

[eyes_on_you]

{
xtype:'combo',
id:'newproject_contractDate',
readOnly :true,
name:'contractDate',
fieldLabel :'合同日期',
allowBlank :false,
blankText:'不允许为空',
mode: 'remote',
displayField:"contractDate",
triggerAction: "all",
store: new Ext.data.JsonStore({
url : "loadcontractDate.action",
fields :[{name:'contractDate',type:'date',mapping:'contractDate.time',dateFormat:'time'}],
root : "items",
baseParams:{
"ownerName":''
},
totalProperty : "results"
})
}
贴不了图，combobox下拉展开之后日期变成
Wed Aug 4 00:00:00 UTC+0800 2010
Thu Jul 1 00:00:00 UTC+0800 2010
怎么把他变成我想要的，y/m/d?