app.module.ts

import { NgModule, LOCALE_ID} from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';
import { AppComponent } from './app.component';
import { LocaleService } from './locale.service';

@NgModule({
  imports:      [BrowserModule],
  declarations: [AppComponent],
  bootstrap:    [AppComponent],
  providers: [
    LocaleService,
    {
      provide: LOCALE_ID,
      deps: [LocaleService],
      useFactory: ($locale: LocaleService) => $locale.get()
    }]
})
export class AppModule { }

locale.service.ts

import { Injectable } from '@angular/core';
import { registerLocaleData } from '@angular/common';

import localeNl from '@angular/common/locales/nl';
import locale_nl_BE from '@angular/common/locales/nl-BE';
import locale_ar_EG from '@angular/common/locales/ar-EG';
import locale_he from '@angular/common/locales/he';
import locale_zh from '@angular/common/locales/zh';

registerLocaleData(localeNl);
registerLocaleData(locale_nl_BE);
registerLocaleData(locale_ar_EG);
registerLocaleData(locale_he);
registerLocaleData(locale_zh);

@Injectable()
export class LocaleService {
  private LOCALE_KEY = 'locale';

  set(locale: string) {
    localStorage.setItem(this.LOCALE_KEY, locale);
  }

  get(): string {
    return localStorage.getItem(this.LOCALE_KEY) || 'en-us';
  }

}