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)?  
Publication date - only for articles? Can it be updated?
seo;google