I think there maybe is a bug in the Graphene Theme
Google, In structured tools - hatom-entry:
Error: Missing required field “updated”
This error occur when Google Snippet cannot find date it was published or last updated.
To solve this?
I think mayby Something like:
<span class="post_date"><?php the_time('j F,Y'); ?></span>
and replace it with
<span class="post_date date updated"><?php the_time('j F,Y'); ?></span>