Dates in the Datetimepicker control appear in the incorrect format when you view a report of SQL Server 2005 Reporting Services with SP2 on a server that is set to a UK locale
http://support.microsoft.com/kb/938823/en-us
In this scenario, the date appears in the mm/dd/yyyy format in the Datetimepicker control. However, you expect that the date appears in the dd/mm/yyyy format.
