[low] first published dates missing

[shawna-slh]

Several pages are missing the first published date, e.g., https://www.w3.org/WAI/tutorials/page-structure/regions/#wai-site-footer
A few still have it, e.g., https://www.w3.org/WAI/tutorials/page-structure/#wai-site-footer

@yatil I think the first published dates got lost with the metafooter. Any suggestions for getting them back, that is, figuring out when was the first published month and year for each?