Please upgrade here. These earlier versions are no longer being updated and have security issues.
Fix to have LastMod time show up (Category DateLastComment --> DateUpdated)
This discussion is related to the Sitemaps addon.
I had to change
'LastMod' => $Category['DateLastComment'], // line 107 in class.sitemaps.plugin.php
'LastMod' => $Category['DateUpdated'], // updated this to correct bug with above column incorrect name.
Since the category table did not have the 1st column name.