redirect date permalink structure

we recently changed our custom permalink structure

from:

/%year%/%monthnum%/%day%/%postname%/
eg, http://domain.com/2011/04/01/articles-headline/

to:

links are only following post name now
/%postname%/

eg, http://domain.com/articles-headline/

what is the best way to redirect links that previously had dates?

eg,

detect: http://domain.com/2011/04/01/articles-headline/

and send/redirect to: http://domain.com/articles-headline/