WPF Format DateTime in TextBlock?

I have a TextBlock thats bound to a DateTime property how do i configurate the format of the date?

From stackoverflow

• There is a string format property available when you are declaring the binding:

  <Textbox Text={Binding Path=DateTimeValue, StringFormat=dd-MM-yyyy} />
  

  (You need to be on .NET 3.5 SP1 for this property to exist)