How to unset a locale variable using localectl?

Under Fedora, I've set a custom locale variable value:

localectl set-locale LC_TIME=en_DK.UTF-8

This modified LC_TIME indeed. Now I'd like to get it back to unset/empty/default state. How do I do that? Preferably, with the same tool that did the change. Both LC_TIME= and LC_TIME="" throw an error.