@silverliebt You can use below solution:
Just navigate to your Theme Options > Misc > use last modified date for post meta data, and turn the option on.
DO note that the modified date does not reflect in yoast and it is issue on their side. However if you do above changes in Meks, then google should pickup your modified date.
Thank you for your reply. I guess it is just an issue related to google crawling, which may have not been done after I updated my site. ( I have already requested index and updated sitemap on CONSOLE week back but still ).
My query is why does the Google snippet of YOAST SEO not show the modified date? In my case it is showing published date only.
For your additional testing, I have checked the date of http://www.wanderisle.com/cebu-coron-tour-package/ link which shows 5th OCT in google, but in YOAST snippet it shows 28th September which was creation date.
