Response to: Confirm Date must be greater than Join Date using customeValidator

Revision 2
With the very less information you have posted , I am posting my most probable guess

if (myDate < myDate2)
                args.IsValid = true;
            else
                args.IsValid = false;

Date of join should be less than the confirmation date. Only in that case the .IsValid is true

NOTE: Instead of using javascript, you can use the CompareValidator in asp.net