DateTime.Min/MaxValue as SQL data source default parameter value?

[Homer J. Simpson]

When I try to use the following:

<asp:SqlDataSource ID="SqlDataSource1" runat="server"
ConnectionString="<%$ ConnectionStrings:csToolbar %>"
SelectCommand="spGetValuesForDateRange" SelectCommandType="StoredProcedure">
<SelectParameters>
<asparameter DefaultValue="<%= DateTime.MinValue %>"
Name="FIRSTDAY" Type="DateTime" />
<asparameter DefaultValue="<%= DateTime.MaxValue %>"
Name="LASTDAY" Type="DateTime" />
</SelectParameters>
</asp:SqlDataSource>

....I get an error implying that DateTime.M[in]|[ax]Value is invalid--ASP.NET
seems to think I'm trying to use strings. I can't figure out the proper
syntax.