SSRS Date Formatting and European numbers

Question

I created a number of fields in order to sort out why I couldn't easily format my date field as a date (it is date in the database, but with FetchXML it seems to lose the formatting. I know this should be accomplished with nested formulas, but since I kept having errors, I wanted to understand where the problem was exactly.

Date is "CreatedOn" : dd/MM/yyyy hh:mm:ss I created a field called "SignUpLeft" with this expression:

=Left(Fields!createdon.Value,10)

I created another field, and I called this "Cdate": =Format(CDate(Fields!SignDateLeft.Value),"dd/MM/yyyy")

I have my report sorting by the "Cdate" field, but it is sorting by the Day, rather than by the month (see pic below.) I have changed the report attribute localization to "es-es".

What else can I do to get the date formatted correctly, in order to sort.