What happens when you choose a default country during installation? In the last step when you install Drupal 8 under "Configure site" you can choose a "default country":



However no clues are provided about the option...


What happens when you choose a default country for the site?
And what happens when you just leaves it as "none"?
In drupal core this is only used for date and time formats. If you leave it empty you can set it later in the admin menu: 

/admin/config/regional/settings