pretty url

I want to write a permalink like /year/month/day/title, code is as follows:

self.permalink = “#{now.year}/#{now.month}/#{}/#{title}”

in the view, I use restful url post_path(@post). And in the html source code, the url is /posts/2008%2F4%2F30%2FTest

You can see, the ‘/’ is replaced by “%2F”, which is not I expect.
How not to replace the ‘/’ with “%2F”?

use url_for or just hard code it into the view [?]

is there any graceful method?

url_for or what not