How to to add a default date time parameter for my SSRS parameter?

I am trying to add a default date time parameter to my SSRS parameter. 1. The condition is to date parameter should be defaulted to 01/01/YYYY 12:00:00 AM (YYYY is current year). 2. The condition is from date parameter should be defaulted to 12/31/YYYY 11:59:00 PM (YYYY is current year).I have tried cdate,dateformat,FormatDateTime nothing worked(apparently I am making some sort of mistake).This for AXSome of the things I tried =CDate(Format("01/01/year(today())") & " 12:00 AM")=Format(Parameters!MyParameter.Value, "01/01/2013 12:00") (I know it works for only one year but for now atleast)