I've just noticed that one of the categories in my XML sitemap is set to Last Modified 1970-01-01 00:00.
Has anyone else experienced this? I've tried disabling/enabling the XML sitemap and editing the contents of the categories.
I noticed there is a similar post to this , but it is from a while ago and it remains unanswered.
Example at http://www.chaiselongue.co.uk/sitemap_index.xml. It's the /product_tag-sitemap.xml sitemap (drawn from woocommerce).
Any help appreciated! :)