Month names not appearing correctly

i installed a language pack, it works well except the month names in Admin->Customers->Orders
Date Purchased: Friday 19 October 2012

i don't know why it always keeps "Friday" and "October" even i convert to the other language

i checked the language file in /admin/includes/languages/, and i tried chaging it to
define('_OCTOBER', 'Hello Test');
but it seams the month of date purchased is not from this file,

what do i fix this?

The days and months are not stored anywhere, they are generated by php and determined by the locale setting (as found in the main english.php or whatever_language.php file).

The locale setting also depends what server (windows/unix) you are running Zen Cart on.

This info should cast some light on this:
http://www.zen-cart.com/showthread.php?133111-locale-not-available-on-local-server-maybe