Calculate Time difference when using HTML5 Time TextBox in ASP.Net

<tr>
    <td>
        <asp:Label ID="Label10" runat="server" Text="From Time"></asp:Label>
    </td>
    <td>
        <asp:TextBox ID="TextBox3" runat="server" TextMode="Time"></asp:TextBox>
    </td>
    <td>
        <asp:Label ID="Label11" runat="server" Text="To Time"></asp:Label>
    </td>
    <td>
        <asp:TextBox ID="TextBox6" runat="server" Width="144px"></asp:TextBox>
    </td>
</tr>

Hi

I have two textbox with from time and to time. how to  calculate total time between from time and to time textboxes.

thanks is advance