Calendar 9.0 - don't show GMT

I entered a new appointment in Calendar today, and noticed for the first time that the time showed GMT as well as EST, thus: "2:30 PM (7:30 PM GMT)" This hasn't happened before. I'm not much interested in the time in Greenwich, England. How do I get Calendar to stop showing GMT? I've looked in Settings and can't find anything that seems to make a difference.

(This is on an iMac running macOS Sierra 10.12.6)