Sitemap Lastmod Problems (Invalid Date)

[coert_g]

Running through Google's search console, we noticed that majority of our indexed content returns an error. The problem being that our site was migrated from another CMS and it appears all pages which haven't been modified since that initial migration has a NULL database value for the modified date field. 

The result is that when the sitemap is built, it inserts an invalid lastmod date into the sitemap for that URL (1-1-1970)

What would be the best way to go about resolving this? Would running a replace on the null values (with a recent date) be the best way?

[Sonya*]

I would set the modified date to publish date and not the recent date.

[opentype]

35 minutes ago, coert_g said:

… we noticed that majority of our indexed content returns an error. The problem being that our site was migrated from another CMS …

What is that error exactly? 
Have you set up forwarding for the old URLs? That would be way more important than anything concerning the sitemap. 

[coert_g]

1 minute ago, opentype said:

What is that error exactly? 
Have you set up forwarding for the old URLs? That would be way more important than anything concerning the sitemap. 

The URLs are all forwarded correctly, the errors just revolve around the lastmod date that is put into the sitemap XML files. Each URL has a lastmod date attached to it, and Google sees majority of ours as 1970-1-1, which then in turn gives the following error: "An invalid date was found. Please fix the date or formatting before resubmitting."

There are thousands of these errors, as a lot of our content hasn't been modified since the migration.

We essentially just need a way to feed in a valid date into the modified date field across our tables.

[bfarber]

I would recommend submitting a ticket so we can take a look.