FYI: Group Policy Preferences > Regional Settings.
If you've been wondering how to make that red underlining green:
F5: Mark all settings on the page as "green" (apply all)
F6: Mark current settings on the page as "green" (apply this settings)
F7: Mark current settings as "red" (don't apply this setting)
F8: Marks all settings on the page as "red" (don't apply)
F3: Gives a list of available variables.
Found here: Florian’s Blog » When I create a Regional Options Preference, my settings are not saved!