Once and are Done, reference data will have APIs which return configurable system locale settings. The UI does have similar default settings, but should primarily use the ones from reference data and use the default settings as backup if the API does not return data.
Refactor currency/number related UI components to use currency settings from API, if necessary
Refactor date related UI components to use date settings from API, applying timezone in particular, so that when dates are shown in the UI, they are not based on the browser's timezone
If the API does not return certain settings, the UI components should use the corresponding defaults it has in the UI configuration