Date Exclusion Plugin
We have added to our plugin repository an updated Date Exclusion Plugin called date-exclusion-seo.
Most of my traffic from search engines is through old posts. This is especially true if like us you have been blogging for a long time, and have lots and lots of content. I wanted to remove the date from my old posts only, but I could not find a plugin that worked, so I modified the original plugin to work on WordPress 2.7.X .
There has been plenty of discussion on the matter from various blogging sites including Daily Blog Tips and Problogger.
You can get the plugin here.