Binding a datetime value is just as straight forward as binding any other data type to your grid, here is a quick reference however on how to properly format it:

When binding to a BoundField:

<asp:BoundField HeaderText="Date Finalised" 

                HtmlEncode="false" 

                DataField="DateAgreementCompleted" 

                DataFormatString="{0:yyyy/MM/dd}" />

The only thing to note here is the DataFormatString and the HtmlEncode property. The DataFormatString works in exactly the same way you would format a datetime when using .ToString (here's a quick reference on string formatting in c#) and the HtmlEncode ensures that the data is displayed properly and not encoded by asp.net.

When binding to a TemplateField:

<asp:TemplateField HeaderText="Date Finalised">

    <ItemTemplate>

        <asp:Label ID="lblDate" runat="server" 

            Text='<%# Bind("DateAgreementCompleted", "{0:yyyy/MM/dd}") %>' />

    </ItemTemplate>

</asp:TemplateField>