需要设置HtmlEncode="False". 微软的说明: When the HtmlEncode property is true, the value of the field is HTML encoded to its string representation before the formatting string is applied. For some objects, such as dates, you might want to control how the object is displayed with a formatting string. In those cases, you must set the HtmlEncode property to false. http://msdn2.microsoft.com/en-us/library/system.web.ui.webcontrols.boundfield.dataformatstring.aspx
微软的说明:
When the HtmlEncode property is true, the value of the field is HTML encoded to its string representation before the formatting string is applied. For some objects, such as dates, you might want to control how the object is displayed with a formatting string. In those cases, you must set the HtmlEncode property to false. http://msdn2.microsoft.com/en-us/library/system.web.ui.webcontrols.boundfield.dataformatstring.aspx
还一个一个方法是，将日期列变模板列后。
在HTML中
<%#Eval("date"),{0:D}%>
这样也可以