Software Upgrade causes language change in Login screen and shutdown popup window I am running MacOS 10.13.6. I upgrade Security Update 2018-003, Command line Tools (macOS High Sierra version 10.13) for Xcode, Safari to the latest version one day ago. The weird thing is even if the system still shows English in most parts, but the Login Screen and shutdown popup window display Chinese now. I checked System Preferences > Language &amp; Region > I have only English listed in Prefered languages (The region is China because I am currently in China). Can anyone please let me know how to change login screen and shutdown popup window back to show English? Thanks a lot.
I found the solution. In terminal, execute the following command

sudo languagesetup


choose English in the command prompt and then logout and login again or reboot. The language in Login Screen will become English.