I also have problem with it but I manage to correct it with:
1. Setting Globalization(true) to telerik ScriptRegistrar. Its inside _AdminLayout.cshtml in administration project.
@(Html.Telerik().ScriptRegistrar()
.jQuery(false)
.jQueryValidation(false)
.Globalization(true)
)
2.
Next you need to change validation test from "(?:\d+|\d{1,3}(?:,\d{3})+)(?:\.\d+)" to "(?:\d+|\d{1,3}(?:\.\d{3})+)(?:,\d+)"
3. In global.asax I remove fixed culture setting
From
//always set culture to 'en-US'
//we set culture of admin area to 'en-US' because current implementation of Telerik grid
//doesn't work well in other cultures
//e.g., editing decimal value in russian culture
var culture = new CultureInfo("en-US");
Thread.CurrentThread.CurrentCulture = culture;
Thread.CurrentThread.CurrentUICulture = culture;
To
var workContext = EngineContext.Current.Resolve<IWorkContext>( );
if( workContext.CurrentCustomer != null && workContext.WorkingLanguage != null )
{
var culture = new CultureInfo( workContext.WorkingLanguage.LanguageCulture );
Thread.CurrentThread.CurrentCulture = culture;
Thread.CurrentThread.CurrentUICulture = culture;
}
Remark. Its about decimal sign (not date). (I did not try date but It may also work for date).
