Which build are you using? The masked input controls, by default, set the CultureInfo.CurrentCulture, which will be the one on your machine. You can also change the current culture using the Thread.CurrentThread:
System.Threading.Thread.CurrentThread.CurrentCulture = new CultureInfo("en-US");
Please note that this has to be done before the control is initialized.
the Telerik team
Sharpen your .NET Ninja skills
! Attend Q1 webinar week and get a chance to win a license! Book your seat now >>