Warning: Missing required field "updated"

Google’s Test Tool for structured data reports the above error when using twenty thirteen, twelve, and eleven.

I need to change the theme’s functions.php to resolve this error – which is baaad.

Read more about it here: http://www.technosultants.com/blog/warning-missing-required-field-updated-wordpress

Is there any other way around? Child themes don’t work here, because it is the funcitons.php.

koem