Indsæt datetime i DB

Jeg prøver indsætte en post i en databasen, men datetime bliver ikke sat bliver NULL, de andre ting bliver sat rigtigt ind.
Hvad gør jeg forkert?

<asp:SqlDataSource id="CreatUser" runat="server"
    ConnectionString="<%$ ConnectionStrings:BloodlineConnection %>"
    SelectCommand="SELECT username, password, email, dateCreated FROM users"     
    InsertCommand="INSERT INTO users (username, password, email, dateCreated) VALUES (@username,@password,@email,@dateTime)">
    <SelectParameters>
    </SelectParameters>
    <InsertParameters>
        <asp:ControlParameter ControlID="reg_name" Name="username" PropertyName="Text" />
        <asp:ControlParameter ControlID="reg_pass" Name="password" PropertyName="Text" />
        <asp:ControlParameter ControlID="reg_mail" Name="email" PropertyName="Text" />
        <asp:Parameter Name="dateTime" Type=DateTime />
    </InsertParameters>
</asp:SqlDataSource>