Broke Permalinks

I totally broke it. I changed my permalinks settings in my dashboard from Default to Day and name. Know when I click on the titles of posts or pages I get a website error.

This website has been running on default for about 4 years, and just recently change it to Day and Name and get “Web Page Can’t be Found”.

If I switch it back to default everything works. Why can’t I change it to day and name and make it work. Do I need to run some of type of plugin or script to populate the change through the SQL database.

Any help greatly appreciated.