I want to change the Datetime parameter to DDMMYYYY format.its default value is MMddYYYY.when user will select date from date picker the date should be disp
You dont even need to set the language to user!Language. SSRS will pick up the DateFormat from the local users regional settings.

But obviously you dont have a lot of control over this and if your customer is screaming for this format, they may not have their PC set with these settings?
good luck!
This report belows' language is set to en-au (which is dd/mm/yyyy)
