XF 2.1 User last post date

[dwooding]

Is there a way to reference a user's last post date, ex - if user's last post date is greater than 2 weeks from today, then ...?

Trying to create an advertisement that displays if someone's last post is more than 2 weeks ago. Something like this ...

<xf:if is="{$xf.visitor.last_post_date} < strtotime('2 weeks ago')">
...

Thanks