macOS sets a specific program locale

$ # Get the application bundle identifier
$ mdls -name kMDItemCFBundleIdentifier /Applications/QQ.app
kMDItemCFBundleIdentifier: "com.tencent.qq"

$ # Set the application language code (ISO 639-2)
$ defaults write com.tencent.qq AppleLanguages '("zh\_CN")'

References