I'm having a problem indexing my "WP SEO by Yoast" generated sitemaps in Google Webmaster Tools. It appears to be because of an invalid date.
It shows for Last Mod.: (-0001-11-3 T00:0)
Parent tag: url
"An invalid date was found. Please fix the date or formatting before resubmitting." My question is, how do you fix the date?
This is the one I get the error in:
and this is the main sitemap: