I can't see the decrement month sign (<) in the calendar, this works in windows but not in Ubuntu ff2. I've checked the tests and there it looks fine. I can't understand why it ain't working... Here's my "clean" test:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="sv" lang="sv">
<head>
<title>Test</title>
<script type="text/javascript" src='./dojo_svn/dojo/dojo.js.uncompressed.js' djConfig="parseOnLoad: true, isDebug: true"></script>
<script type="text/javascript">
dojo.require("dojo._firebug.firebug") ;
dojo.require("dojo.parser");
dojo.require("dijit.form.DateTextBox");
</script>
<link href="./dojo_svn/dojo/resources/dojo.css" type="text/css" rel="stylesheet" />
<link href="./dojo_svn/dijit/themes/tundra/tundra.css" type="text/css" rel="stylesheet" />
<link href="./dojo_svn/dijit/themes/tundra/tundra_rtl.css" type="text/css" rel="stylesheet" />
</head>
<body class="tundra" style="margin: 2em;">
<fieldset class='mg_form'>
<legend>Date</legend>
<table>
<tr>
<td>
DateTextBox:
</td>
<td>
<input type="text"
name="my_date_text_box" id
="my_date_text_box"
value="2007-07-15"
maxsize="10"
style="text-align: right;"
size="10"
dojoType="dijit.form.DateTextBox" required="true" />
</td>
</tr>
</table>
</fieldset>
</body>
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="sv" lang="sv">
<head>
<title>Test</title>
<script type="text/javascript" src='./dojo_svn/dojo/dojo.js.uncompressed.js' djConfig="parseOnLoad: true, isDebug: true"></script>
<script type="text/javascript">
dojo.require("dojo._firebug.firebug") ;
dojo.require("dojo.parser");
dojo.require("dijit.form.DateTextBox");
</script>
<link href="./dojo_svn/dojo/resources/dojo.css" type="text/css" rel="stylesheet" />
<link href="./dojo_svn/dijit/themes/tundra/tundra.css" type="text/css" rel="stylesheet" />
<link href="./dojo_svn/dijit/themes/tundra/tundra_rtl.css" type="text/css" rel="stylesheet" />
</head>
<body class="tundra" style="margin: 2em;">
<fieldset class='mg_form'>
<legend>Date</legend>
<table>
<tr>
<td>
DateTextBox:
</td>
<td>
<input type="text"
name="my_date_text_box" id
="my_date_text_box"
value="2007-07-15"
maxsize="10"
style="text-align: right;"
size="10"
dojoType="dijit.form.DateTextBox" required="true" />
</td>
</tr>
</table>
</fieldset>
</body>

Solved - wrong DOCTYPE
Changed to:
"http://www.w3.org/TR/html4/strict.dtd">
and suddenly it works like a charm :-)