Localize Utilities

Device locale, timezone, and formatting utilities with react-native-localize fallback.

iOSAndroid

Overview

The localize module provides device locale detection, timezone, date/number/currency formatting, and measurement system detection. It requires react-native-localize for accurate native locale data and falls back to Intl APIs when unavailable.

Installation

npx expo install react-native-localize

Required Packages(1 package)

pnpm add react-native-localize

Expo Configuration

Add react-native-localize as a plugin in your app.config.ts with the locales your app supports:

{
  plugins: [
    [
      'react-native-localize',
      { locales: ['en', 'tr', 'de', 'fr'] }
    ]
  ]
}

Note: Without this plugin config, locale detection may not work correctly on iOS. The locales array determines which languages your app declares support for.

Usage

import {
  getDeviceLocale,
  getDeviceLanguage,
  getDeviceCountry,
  getDeviceTimeZone,
  uses24HourClock,
  usesMetricSystem,
  formatDate,
  formatNumber,
  formatCurrency,
} from '@/lib/docyrus/localize';

// Device info
const locale = getDeviceLocale();        // 'tr-TR'
const lang = getDeviceLanguage();        // 'tr'
const country = getDeviceCountry();      // 'TR'
const tz = getDeviceTimeZone();          // 'Europe/Istanbul'
const is24h = uses24HourClock();         // true
const metric = usesMetricSystem();       // true

// Formatting
formatDate(new Date(), { dateStyle: 'long' });   // '5 Mart 2026'
formatNumber(1234.56);                            // '1.234,56'
formatCurrency(99.99, 'TRY');                     // '₺99,99'

API Reference

Device Info

Function	Return Type	Description
`getDeviceLocale()`	`string`	Full locale tag (e.g., `'tr-TR'`). Falls back to `'en-US'`
`getDeviceLanguage()`	`string`	Language code (e.g., `'tr'`). Falls back to `'en'`
`getDeviceCountry()`	`string \| undefined`	Country code (e.g., `'TR'`)
`getDeviceTimeZone()`	`string`	IANA timezone (e.g., `'Europe/Istanbul'`). Falls back to `'UTC'`
`uses24HourClock()`	`boolean`	Whether device uses 24-hour clock
`usesMetricSystem()`	`boolean`	Whether device uses metric system
`getPreferredLocales()`	`string[]`	All preferred locale tags

Formatting

Function	Parameters	Description
`formatNumber(value, options?, locale?)`	`number, Intl.NumberFormatOptions?, string?`	Locale-aware number formatting
`formatDate(date, options?, locale?)`	`Date, Intl.DateTimeFormatOptions?, string?`	Locale-aware date formatting
`formatCurrency(value, currencyCode?, locale?)`	`number, string?, string?`	Currency formatting (default: `'USD'`)
`getCurrencySymbol(currencyCode)`	`string`	Get currency symbol (e.g., `'₺'` for `'TRY'`)

Fallback Behavior

Feature	With `react-native-localize`	Without (Intl fallback)
Locale detection	Device's preferred locale list	`Intl.DateTimeFormat` resolved locale
Timezone	`RNLocalize.getTimeZone()`	`Intl.DateTimeFormat` resolved timezone
24h clock	`RNLocalize.uses24HourClock()`	AM/PM presence check
Metric system	`RNLocalize.usesMetricSystem()`	Country code heuristic (US, LR, MM → imperial)

Compatibility

Platform	Support
Expo Go	Yes
Dev Client	Yes
Bare RN	Yes (auto-linked)

Localize Utilities

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