I'm getting missing: updated error with Google Webmaster

Hi,

I'm running Dynamik theme for Wordpress. Looking at Google Webmaster it's showing 'missing:updated' against all of my posts. I found this solution http://nepallica.com/fix-google-rich-snippets-warning-missing-required-field-wordpress/ but can't find the simple.php file they say you need to modify. Any help or pointers appreciated! Thanks