How to use the after=”” shortcode argument

Hi,

First of all, thank you for this plugin. So far it seems to work wonderfully.
In particular, I have seen that one of the possible arguments to add to the shortcode is the ‘after’ a date.

I would like to show posts in ascending order starting one year ago. How should I use the ‘after’ in this context?

This is my shortcode so far:

[rpwe limit=”10″ order=”ASC” post_type=”post” post_status=”publish” thumb=”true” thumb_height=”60″ thumb_width=”60″ thumb_align=”rpwe-alignleft” date=”false” styles_default=”true” after=”???????????”]

Thanks so much for your help!