What meta tag do you use to provide Google with a publication date?

Question

Possible Duplicate:
How does Google recognize publish date of a post

I read about the Dublin Core Metadata Initiative and some spotty documentation from Google, but I can't find an official resource.

Thanks in advance.

Solution

As mentioned in comments, this Question appears to cover all bases:
How does Google recognize publish date of a post

Just to add... there are probably several methods that Google uses in order to determine the publish date (if any) of an article. XML sitemaps and RSS feeds are commonly cited as possible sources, however, Google does often appear to simply get the publish date from on-page content - which is not necessarily correct!

For example... I have a site that has a submitted sitemap.xml and many pages show a publish date in the SERPs. However, the publish date showing in the SERPs does not match the <lastmod> date in the sitemap - for any page. In all cases the publish date that shows in the SERPs is a date that appears on the page itself - which in many cases is not actually the publish date of that page!

Just an observation... On all the pages that have a publish date in the SERPs, that date appears somewhere in the content of that page. If it doesn't appear on the current page, then in Google's cached version there is a date. This always appears to trump any date that might appear in the RSS feed or Sitemap.

Can you find any pages that have a publish date in the SERPs where that date does not appear in-page?

Comments

[MrWhite]

Related: How does Google recognize publish date of a post

[ezequiel-garzon]

Thanks! I think that's more than just related: that answers my question. Please post it as an answer so I can mark it appropriately. (I thought the meta tags played a critical role, but I going over sitemaps.org I guess not.)

[ezequiel-garzon]

That unpredictable, undocumented behavior is pretty disappointing, above all considering the joint effort the industry has put behind sitemaps.org... Out of curiosity, have you found a common pattern? For instance, I imagine the first date to appear may be given the most weight. Right?

[MrWhite]

If there are multiple dates on a page then Google appears to pick the date that is more closely linked to the article, not necessarily the first date on the page - which is actually correct in many cases. See my answer in that other question with regard to marking up the date using microformats. I've updated my answer with an observation.