toLocaleString wrong format on Android

Is this a bug report?

Yes

Have you read the Contributing Guidelines?

Yes

Environment

Environment: OS: macOS Mojave 10.14.1 Node: v11.1.0 Yarn: 1.12.3 npm: 6.4.1 Watchman: 4.9.0 Xcode: Xcode 10.0 Build version 10A255 Android Studio: 3.1.3 Build #AI-173.4819257

Packages: (wanted => installed) react: 16.4.1 => 16.4.1 react-native: 0.56.0 => 0.56.0

Target Platform: Android (8.0)

Steps to Reproduce

1. Open a fresh React Native project
2. Make sure you’re not debugging JS remotely
3. Try to use toLocaleString on a Date() object

  let formatted = new Date('2017-11-17T10:59:30.527Z').toLocaleString('de-DE', {
    timeZone: 'Europe/Zurich',
    year: 'numeric',
    month: 'numeric',
    day: 'numeric',
    hour: 'numeric',
    minute: 'numeric',
  })

1. Either write up a simple component to display text or do an alert/console.log with the aforementioned variable.

Expected Behavior

The expected string should be as follows:

Imput: 2017-11-17T10:59:30.527Z -> Output: 17.11.2017, 11:59

Actual Behavior

The resulting string is as follows:

Imput: 2017-11-17T10:59:30.527Z -> Output: Fri Nov 17 11:59:30 2017

My contention is that this is an issue with the underlying JS engine that Android uses, and handles it differently as opposed to the integrated JS engine on iOS, hence the variance in the date format. For this reason if you open a remote debugged, say on Chrome, you will actually get the correct format, due to the different JS engine handling it, but if you switch off the debugger and resume using the application whilst not debugging remotely, the incorrect format will be shown.

Reproducible Demo

Here’s an example Expo project that shows the behaviour, toggle between iOS and Android to see the difference in the output.

https://snack.expo.io/Bk3unwhyM

EDIT: Updated environment in which this is still reproducible.

[oriharel]

This issue must exist.

[kholiavko-roman]

Issue still present in the latest version.