There are two items included with the Localization setting.
Language and Time zone.
Both are set site-wide.
This is primarily an Admin perk. If there is a system generated message, it will be shown in the language of your choice.
The Content on your site will be in whatever language you enter it regardless of the Language setting.
For users who are logged in, each can have their own system language preference.
Note: SimpleUpdates is glad to add new language files for our system, but would need a volunteer who speaks the new language to check the machine translation for accuracy. We use a language editing system: POEdit. If you would like to improve or assist with our translation files, download this free program and contact us with your offer to help. We appreciate it!
You can set the time zone for your website, which will affect some calendar functions.
To locate your time zone, look for the large area where you are located and then the largest nearby city.
For example: here in our little town of Berrien Springs Michigan, the best option is America/Detroit.
Berrien Springs is on the far western side of the Eastern Time zone. America is the large area and Detroit is the largest city near us that is in the Eastern Time Zone.
Chicago or Indianapolis would be closer to us in miles, but they are Central time zone and therefore will not work for us.
Admittedly this is not the easiest item to set and the list is quite long as it covers the entire world, but once it is set, you don't have to deal with it again.