Showing each node's creation date but in the content-list (instead on in each node)?
I believe the purpose of this module Administration Views is exactly what you are asking for. 
Once you install it, it will allow you to override your "content" page.
This way you can add extra columns, sorting and filters to that page, using the Views UI.

The View you are looking for is called Administration: Nodes (at least in D7) and if you edit that and add fields, they will show up on the content overview page. (comment by @Neograph734)


You would need to edit this view, by navigating to the admin/structure/views/view/admin_views_node URL. 
Add the "Content: Post date" to the field of that view 
Configure the new field; set the Date format to "Short" and possible renaming its label to sth like "Created". 
You can optionally rearrange your columns and also make the new "Created" column Sortable in the Table format setting
Save your view and visit the admin/content URL, it should now look similar to this: 


Hope this helps!