# Locale and timezone (/docs/e2e/conditions/locale)



`device.locale` and `device.timezone` change what the app formats dates, numbers and strings with. Both take `null` to put the setting back, and both are undone when the test ends.

```ts
await device.locale("fr-FR");
await device.timezone("Asia/Tokyo");
await app.open(); // iOS: the next launch picks both up
```

| Member                               | Does                                 |
| ------------------------------------ | ------------------------------------ |
| `locale(tag \| null, { bundleId? })` | a BCP 47 tag (`"fr-FR"`) for the app |
| `timezone(tz \| null)`               | an IANA name (`"Asia/Tokyo"`)        |

On iOS, set both before `app.open()`, or relaunch the app. Android changes them live; the per-app locale needs Android 13+ ([per platform](/docs/sims/conditions/locale#per-platform)).

## In a suite [#in-a-suite]

```ts title="warden.config.ts"
conditions: { locale: "fr-FR", timezone: "Asia/Tokyo" },
```

By hand with `warden ui locale` and `warden ui timezone`: [Locale and timezone on a simulator](/docs/sims/conditions/locale).