Problem in User Guide, set_cookie

[eluser]timotheus[/eluser]
Helped from:
http://ellislab.com/forums/viewreply/804985/

The manual states that the set_cookie method only requires the cookie name and cookie value, but this is incorrect. You MUST specify an expiration time, otherwise it creates the cookie that expired 24 hours ago.

I could be missing something, but my cookie section of the config.php file is the default.