Configuring the Settings

If you want your permalink to show the year, month, day, category, and post

name, select the Custom Structure radio button in the Customize Permalink
Structure page and type the following tags in the Custom Structure text box:

/%year%/%monthnum%/%day%/%category%/%postname%/

By using this permalink format, the link for a post made on February 1, 2011, called WordPress All in One For Dummies and filed in the Books I Read
category, would look like this:

http://yourdomain.com/2011/02/01/books-i-read/wordpress-all-in-one-for-dummies/

Be sure to include the slashes before tags, between tags, and at the very end of the string of tags. This format ensures that WordPress creates correct, working permalinks by using the correct re_write rules located in the .htaccess file for your site. (See the following section for more information on re_write rules and .htaccess files.)
Changing the structure of your permalinks in the future affects the perma-
links for all the posts on your blog . . . new and old. Keep this fact in mind if
you ever decide to change the permalink structure. An especially important
reason: Search engines (such as Google and Yahoo!) index the posts on
your site by their permalinks, so changing the permalink structure makes
all those indexed links obsolete.
Don’t forget to click the Save Changes button at the bottom of the Customize
Permalink Structure page; otherwise, your permalink changes aren’t saved!