Was sent an email to upgrade my Heroku stack to Heroku-16 from Cedars-14(deprecated), heroku apps:info shows you what stack you're on. In Heroku Article - Upgrading to Latest Stack there are different sections from testing app on new stack to straight upgrade with even a section to rollback just in case it all blows up in your face.
I went ahead and upgraded.
heroku stack:set heroku-16 -a <app name> will set you up, but will not take effect until you push your app to Heroku.
I thought of no changes to make at the moment, but was pleasantly surprised you can create an empty commit so you can push right away. Seriously, I found this to be awesome which is why I'm writing this, a note to self if you will.
git commit --allow-empty -m "upgrade to heroku-16" followed by, of course, git push heroku master
At this point app should be running on latest stack, but of course check on it and make sure all is working as it was before the upgrade.