You could pass through the $post['created'] to the theme layer by adding something like this inside qa_post_html_fields(...) in qa-app-format.php:
Then in the appropriate function in your advanced theme file, check:
((time() - @$this->content['q_view']['created_raw'])<60)
// output whatever you want
The 60 in the code above means this will only be displayed on questions which are less than 60 seconds old, so change that to whatever you want.
Considering a few questions that have appeared like this, methinks it is time that qa_post_html_fields(...) simply passes the entire raw information about the $post through to the theme layer. Will do this for 1.2.1.