This meta tag is for pages that have a significant amount of information that's obsolete. If someone updates the page and decides that it's now up to date, then they can delete the tag. If the page has only been partially updated then leave the tag.
https://arbital.com/p/out_of_date_meta_tag
by Alexei Andreev Oct 21 2015 updated Jul 21 2016
Meta tag used when the page has a lot of information that's obsolete
This meta tag is for pages that have a significant amount of information that's obsolete. If someone updates the page and decides that it's now up to date, then they can delete the tag. If the page has only been partially updated then leave the tag.