This Plugin changes the ‘freshness ‘ that bbPress displays on topic and forum lists (eg 4 hours ago) to the date of the last post to that forum or topic (eg 17th January 2014 at 5.15pm).
It also allows you to set the heading for this new date format.
The existing (bbpress) Recent Topics widget works with date, but a revised Recent Replies Widget to display the date format called (Last Post) Recent Replies is included.
This plugin is available for download for your site.