Publication date - only for articles? Can it be updated?

Question

In Google's search results there are often publication dates of articles. Google finds this date on its own or takes it from DC.date.issued meta tag. Is this date only supposed to be displayed for articles or can be used for other pages?

Let's say I have a website which presents list of local companies. Such list is useless if it's not regularly updated. I think it would be wise to put the update date next to the results so the user knows the list is current. Can I "legally" use the DC.date.issued for that? What if I am updating page and its content does not change (because local companies stayed the same after last update), is it "legal" to change publication date of such page (I am worried that Google might see something suspicious in publication date changed and webpage content remaining the same)?

Answer 1

This can be accomplished by using Structured Data. You can use something like the following to set the update date:

<span class="entry-date updated"><?php echo get_the_date(); ?></span>

This is a WordPress example but the concept is the same.

You can also put the update date in your meta description. This could help with conversations as well. Something like:

LAST UPDATED (12/15/14) - [Page descriptioin]

Answer 2

You need to change/update the content. If you just change the dates you will be penalized, as stated here.