Problems with date configuration

Hi, I had an application in which I used postgres 7.4, and then only thing refering to date was:

     datestyle = 'ISO,European'

everything else was commented. Now I have had to change the OS and I've installed postgres 8.1.3, but this configuration is different, it's something like:
   
    lc_monetary = 'en_US.UTF-8'                  
    lc_numeric = 'en_US.UTF-8'                    
    lc_time = 'en_US.UTF-8'  


and evrything else is commented, including the line which references the datestyle. But in the comment it says #datestyle = 'iso, mdy'. Someone can help me to make it works in the same way?

Thanks.

Fabi