MediaWiki article change dates displayed in Google SERPs - why?

[badbadmonkey]

Google is showing the last-modified date in all SERP entries for my MediaWiki install, like:

Article (Wiki)
1 May 2009 ... description text description text description text description
text description text description text description text description text...
www.domain.com/wiki/Article

This isn't desirable because the articles are not time-sensitive nor updated all that often, so the info is useless and detracts from the description text size.

Any idea why Google is deciding to do this? I notice that my MediaWiki articles have no meta tags in the header to do with this... the only place the date appears is the label at the bottom -

<li id="lastmod"> This page last modified on 1 May 2009</li>

This must be the reason, before I take steps to remove it (which isn't really desirable, as a small label at the bottom of the page is okay!), anyone see if I'm missing something?

[tedster]

I think you've got it figured out - I'd say remove that line and see if it fixes your issue.