The date isn’t output on the post grid in Dyad so it wouldn’t be possible to display them without creating a child theme, which isn’t possible on WordPress.com.
These forums are for folks running the WordPress software on their own hosting, not on WordPress.com. If you need further help with your theme on WordPress.com, feel free to post in the themes forum here:
https://en.forums.wordpress.com/forum/themes
Here are some tips on getting help in the WordPress.com forums: http://en.support.wordpress.com/getting-help-in-the-forums/
You can also access the live chat support option when available here:
https://wordpress.com/help/contact
