[whatwg] date meta-tag invalid

[aykut.sensoy at bild.de]

According to the w3c Validator the  <metaname="date"content="#" /> tag is invalid. In the WHATWG MetaExtensions List there is no registered extension, no specification and no proposal for the date meta-tag.
The only alternative for "date" is a proposal called "created", which however doesn't meet the requirements for registration . For our SEO team the date meta-tag contains some of the most important information about a webpage.
What would be a w3c-valid way to implement a creation date meta-tag in html5?


Kind Regards
Aykut Sensoy