http://stackoverflow.com/questions/5584948/format-date-time-in-xaml-in-silverlight
http://matthiasshapiro.com/2010/05/28/silverlight-4-binding-and-stringformat-in-xaml/
http://www.codeproject.com/Articles/195436/Formatting-text-in-Silverlight-XAML-using-StringFo
http://msdn.microsoft.com/en-us/library/az4se3k1.aspx