I18NManager API

import React, { useState } from 'react';
import { AppRegistry, Button, I18nManager ,Text, View } from 'react-native';

const I18nManagerApp = () => {
    const [response, setResponse] = useState('');
    const [locale, setLocale] = useState('');
    const [timezone, setTimezone] = useState('');

    const displayLocale = () => {
        setLocale(`I18nManager locale value - ${I18nManager.getAppLocale()}`);
    };

    const displayTimezone = () => {
        setTimezone(`I18nManager timezone value - ${I18nManager.getTimezone()}`);
    };

     const updateLocaleSetting = (newLocale: string) => {
         I18nManager.setAppLocale(newLocale);
     };

     const updateTimezoneSetting = (newTimezone: string) => {
         I18nManager.setTimezone(newTimezone);
     };

    I18nManager.addListener(I18nManager.SettingEventName.Locale, displayLocale);
    I18nManager.addListener(I18nManager.SettingEventName.Timezone, displayTimezone);

   return (
         <View>
             <Button title="Display I18n Preferences" onPress={displayI18nPreferences} />
             <Text>{response}</Text>

             <Button title="Set Locale - en-CA" onPress={updateLocaleSetting("en-CA")} />
             <Text>{locale}</Text>

            <Button title="Set App TZ - Paris" onPress={updateTimezoneSetting("Europe/Paris")} />
             <Text>{timezone}</Text>

         </View>
     );
};

export default I18nManagerApp;

I18nManager.getAppLocale();

I18nManager.setAppLocale(locale);

I18nManager.getSystemLocale();

I18nManager.resetLocale();

I18nManager.getTimezone();

I18nManager.setTimezone(timezone);

I18nManager.getSystemTimezone();

I18nManager.resetTimezone();

I18nManager.addListener(eventName, callback);

I18nManager.removeListeners();