...
import { NgModule, LOCALE_ID } from '@angular/core';
import { registerLocaleData } from '@angular/common';
import localeFr from '@angular/common/locales/fr';
registerLocaleData(localeFr);


@NgModule({
  imports: [...],
  declarations: [...],
  bootstrap: [...],
  providers: [
    { provide: LOCALE_ID, useValue: 'fr-FR'},
  ]
})
export class AppModule {}