Thanks for your answer.

I did as suggested, unfortunatly the website and usercontrol's are made by an external company, and some of it crashes now ;-(

Is there any other way to get the DatePicker to 'talk' danish?

What crashes? Any exceptions you can show? 

But if it's their controls that crash, you should really ask them why the controls don't work when placed in a Danish locale. The locale is set in the "default .net way", so they would break in other non-umbraco sites as well, seems a bit odd to me.

Hi Sebastiaan

Thanks for your answer, have been busy so not been able to answer.

Gladly I have the source code for their implementation, so i'll fix the error myself (when i have the time).

Thanks for your help.

Finally I got the time to fix this little problem, by using a 'hack'.

In the masterpages code behind file i added the following code, and the DatePicker has monday as start of week :-)

protected override void OnInit(EventArgs e)
        {
            var scriptManager = ScriptManager.GetCurrent(Page);
            if (scriptManager != null)
            {
                scriptManager.EnableScriptGlobalization = true;
                string Lang = "da-DK";//set your culture here
                System.Threading.Thread.CurrentThread.CurrentCulture = new System.Globalization.CultureInfo(Lang);
            }
        } 

Try my solution at http://our.umbraco.org/forum/developers/extending-umbraco/8268-Change-date-picker-format-in-Umbraco?p=1#comment166799

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