Empty last modified fields in sitemap.xml (Drupal 7). How to fix?

Question

Drupal

There is a site on Drupal 7. For some pages, there is no data in the last modified field
. At the same time, for one type of material, one material in the map is fine, while the other field is empty.
rebuild maps does not help. What could be the problem?

Answer 1

I have empty fields for taxonomy terms in XML Sitemap, map output by drupal.org/project/xmlsitemap module. Here, a person makes his own module to get rid of empty fields in the sitemap for the taxonomy terms Drupal Xml Sitemap Last Modified Date - xandeadx.ru/blog/raznoe/267#comment-5134 , but there seem to be questions. Haven't tried it myself. I support the question, I also have empty dates, in terms.