Display the Last saved date on articles
You can simply edit the view mode you're using, Default, Full or Teaser for example:


Download Display Suite and enable the "Display Suite" and "Display Suite UI" modules.
Go to admin/structure/types/manage/article/display/teaser where "article" is your content type and "teaser" is the view mode.
In the "Layout for article in teaser" fieldset, select the "One column" layout and click Save.





You will now see a lot more fields, provided by the Display Suite module. One of those fields is called Last modified.





Drag that field to the top, and you're done! No custom theming or coding required.


As a side-note: in views, the field you're looking for is called "Changed":