Add post date on Twenty Eleven Theme

Hello,

I am taking care of a blog with a custom twenty eleven theme. However, the posts are not displaying the “posted on” date, as you can see here http://www.access-finance-communication.fr/ptz-relance-immobilier/. I bet there is a short code line to include in single.php, but can anyone tell me what to insert and where ?

Lots of thanks in advanced.

Bert