"svn: syntax error in revision argument" for date formats

Can anyone tell me, using svn on OS 10.7.3 with a tcsh shell , what date formats are accepted? I try to do svn up -r {DATE}

and every time I get this:

svn: Syntax error in revision argument

      

        
        
        
      

    

The formats described here are not accepted: http://svnbook.red-bean.com/en/1.2/svn.tour.revs.html

My last attempt was to check:

svn checkout --revision {2012-02-17} svn+ssh://blah/blah blah
svn: Syntax error in revision argument '2012-02-17'

      

        
        
        
      

    

thank