I can have after more and more tests :
http://www.hkrag.fr/blog/index.php/sample-post/
but too old link p=217 never continue to be Ok

What to write please and where ?
(scuze for my poor english

I have my opinions that I share sometimes in my posts, but I more or less just want to explain how to do stuff. I leave much of the advice stuff to other blogs.

@ Matthijs – First of all, these opinions are from Matt Cutts, the lead guy with the Google search team. If your site wants traffic from Google, his opinions probably matter the most.
Matt also mentioned to make dates visible in your posts, but not in the URL. People should be able to get the date from the post if they want it, though on some of my sites I avoid the date all together because over time posts that stay popular years later can sometimes still be very valid but will lose credibility with readers if they see its a few years old. Really just a judgment call based upon your website and your preferences.

@ Ronny – Great point as well. I’ve also been meaning to test and see if you publish a post then a few days later go in and change it to a different date, if the URL remains the same. I assume it wouldn’t change, but never confirmed. Same goes for people with categories in their post URL’s.