change archive url pattern, remove date from it

hi

I want to remove the /date/ from my archive link

http://mydomain.com/news/date/2008/11/

to make it

http://mydomain/news/2008/11/

how can i do this? and functions.php does not have the definition of wp_get_archives() where are these function source code present? i am using 2.6 version

thank you