I can answer that question as I just did an experiment on this which you can review here: http://www.rlmseo.com/blog/seo-impact-blog-post-dates/

The summary is this:

Assuming no displayed date as a baseline, recent dates (not sure exactly how recent - looks like up to 3-12 months but probably depends on industry, etc) will boost traffic significantly.

Compared to the baseline, distant past publish dates will reduce traffic a good bit.

I would recommend this:

• Display update date instead of publish date.
• If a post is still relevant, update it, maybe even add a disclaimer for your users that the post was first published on x date but has been updated and is current.

We've seen dramatic traffic increases with this strategy and it ensures people know how relevant your post is, which is actually more important than the publish date.

I can answer that question as I just did an experiment on this which you can review here: http://www.rlmseo.com/blog/seo-impact-blog-post-dates/

The summary is this:

Assuming no displayed date as a baseline, recent dates (not sure exactly how recent - looks like up to 3-12 months but probably depends on industry, etc) will boost traffic significantly.

Compared to the baseline, distant past publish dates will reduce traffic a good bit.

I would recommend this:

• Display update date instead of publish date.
• If a post is still relevant, update it, maybe even add a disclaimer for your users that the post was first published on x date but has been updated and is current.

We've seen dramatic traffic increases with this strategy and it ensures people know how relevant your post is, which is actually more important than the publish date.