If you have a GridView control and are are trying to data format a BoundField, you may find your format instructions are being ignored. The fix is to add HtmlEncode="False" to the asp:BoundField. Then the DataFormatString should work.

<asp:BoundField DataField="LastModified" 
  HeaderText="Modified" 
  HtmlEncode="False" 
  DataFormatString="{0:d}" />

Labels: ASP.NET