Add "Posted on" to post date (Twentfourteen)

With the Twentfourteen theme’s defaults the date a post is published is just shown as “March 2, 2016” below the title. How can I change this to instead display “Posted on March 2, 2016”?

This seems like a bad default; my site has an older target audience and I got one comment saying that someone thought that a post announcing an event on March 26th (post date Feb. 29) was announcing the event for Feb. 29.

Thank you.