Styles not rendered when using the SharePoint DateTimeControl in custom pages

When using the SharePoint DateTimeControl in custom pages, the popup calendar is rendered without styles. I don't know why but the problem is that the datepicker.css stylesheet is not referenced as explained on the Rich Finn's blog (http://blog.richfinn.net/2006/12/10/SharePointDateTimeControlDoesNotRenderStyles.aspx).

Have a look on the iframe.aspx page located in C:\Program Files\Common Files\Microsoft Shared\web server extensions\12\TEMPLATE\LAYOUTS.

<%@ Assembly Name="Microsoft.SharePoint.ApplicationPages" %> 

<%@ Page Language="C#" Inherits="Microsoft.SharePoint.ApplicationPages.DatePickerFrame"      %> 

<%@ Import Namespace="Microsoft.SharePoint.ApplicationPages" %> 

<%@ Register Tagprefix="SharePoint" Namespace="Microsoft.SharePoint.WebControls" Assembly="Microsoft.SharePoint, Version=12.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c" %> 

<%@ Register Tagprefix="Utilities" Namespace="Microsoft.SharePoint.Utilities" Assembly="Microsoft.SharePoint, Version=12.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c" %> 

<%@ Import Namespace="Microsoft.SharePoint" %> 

<% SPSite spServer = SPControl.GetContextSite(Context); SPWeb spWeb = SPControl.GetContextWeb(Context); %>

<html dir="<SharePoint:EncodedLiteral runat='server' text='<%$Resources:wss,multipages_direction_dir_value%>' EncodeMethod='HtmlEncode'/>">

    <HEAD>

    <META Name="GENERATOR" Content="Microsoft SharePoint">

    <SharePoint:CssLink runat="server"/>

    <script src="./DatePicker.js"></script>

    <title>Date Picker</title>

    </HEAD>

    <BODY onload="PositionFrame('DatePickerDiv');" onkeydown="OnKeyDown(this);" style="margin:0;">

      <SharePoint:SPDatePickerControl id="DatePickerWebCustomControl" runat="server" >

          </SharePoint:SPDatePickerControl>

    </BODY>

</HTML>

To solve the problem, you have to add manually the reference to the stylesheet.

<%@ Assembly Name="Microsoft.SharePoint.ApplicationPages" %> 

<%@ Page Language="C#" Inherits="Microsoft.SharePoint.ApplicationPages.DatePickerFrame"      %> 

<%@ Import Namespace="Microsoft.SharePoint.ApplicationPages" %> 

<%@ Register Tagprefix="SharePoint" Namespace="Microsoft.SharePoint.WebControls" Assembly="Microsoft.SharePoint, Version=12.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c" %> 

<%@ Register Tagprefix="Utilities" Namespace="Microsoft.SharePoint.Utilities" Assembly="Microsoft.SharePoint, Version=12.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c" %> 

<%@ Import Namespace="Microsoft.SharePoint" %> 

<% SPSite spServer = SPControl.GetContextSite(Context); SPWeb spWeb = SPControl.GetContextWeb(Context); %>

<html dir="<SharePoint:EncodedLiteral runat='server' text='<%$Resources:wss,multipages_direction_dir_value%>' EncodeMethod='HtmlEncode'/>">

    <HEAD>

    <META Name="GENERATOR" Content="Microsoft SharePoint">

    <link rel="stylesheet" type="text/css"href="/_layouts/1033/styles/datepicker.css"/>

    <SharePoint:CssLink runat="server"/>

    <script src="./DatePicker.js"></script>

    <title>Date Picker</title>

    </HEAD>

    <BODY onload="PositionFrame('DatePickerDiv');" onkeydown="OnKeyDown(this);" style="margin:0;">

      <SharePoint:SPDatePickerControl id="DatePickerWebCustomControl" runat="server" >

          </SharePoint:SPDatePickerControl>

    </BODY>

</HTML>