Gridview Date Field Not Updating

Hi - Once again I've been looking at this forever and not able to see the problem.  Have a grid table everything updates except the training date field.  That get's wiped out each time - no matter if something is in it or not.  Everything else updates correctly.

Here's the code: 

<asp:GridView ID="GridView1" runat="server" AllowPaging="True" AllowSorting="True" AutoGenerateColumns="False" DataSourceID="ds1" DataKeyNames="eventID">
<Columns>
<asp:CommandField ButtonType="Button" ShowEditButton="True" ShowDeleteButton="True" />
<asp:BoundField DataField="eventID" HeaderText="ID" SortExpression="eventID" ReadOnly="True">
<HeaderStyle Font-Bold="True" Font-Names="Verdana" Font-Size="Small" />
<ItemStyle Font-Names="Verdana" Font-Size="Small" />
</asp:BoundField><asp:TemplateField HeaderText="Training Date" SortExpression="trainingDate">
<EditItemTemplate>
<asp:TextBox ID="TextBox1" runat="server" Text='<%# Eval("trainingDate", "{0:M/dd/yy}") %>'></asp:TextBox>
</EditItemTemplate>
<ItemTemplate>
<asp:Label ID="Label1" runat="server" Text='<%# Bind("trainingDate", "{0:M/dd/yy}") %>'></asp:Label>
</ItemTemplate>
<HeaderStyle Font-Bold="True" Font-Names="Verdana" Font-Size="Small" />
<ItemStyle Font-Names="Verdana" Font-Size="Small" />
</asp:TemplateField>

<asp:SqlDataSource ID="ds1" runat="server" ConnectionString="<%$ ConnectionStrings:TrainingClassTrackingConnectionString %>" ProviderName="<%$ ConnectionStrings:TrainingClassTrackingConnectionString.ProviderName %>"UpdateCommand="UPDATE [trainingLog] SET  [trainingDate] = @trainingDate
WHERE [eventID] = ?" >

<UpdateParameters>
<asp:Parameter Name="trainingDate" Type="DateTime" />
</UpdateParameters>