You have to pass the locale string as an argument to DatePipe.
var ddMMyyyy = this.datePipe.transform(new Date(),"dd-MM-yyyy");
Pre-defined format options:
1.      'short': equivalent to 'M/d/yy, h:mm a' (6/15/15, 9:03 AM).
2.      'medium': equivalent to 'MMM d, y, h:mm:ss a' (Jun 15, 2015, 9:03:01 AM).
3.      'long': equivalent to 'MMMM d, y, h:mm:ss a z' (June 15, 2015 at 9:03:01 AM GMT+1).
4.      'full': equivalent to 'EEEE, MMMM d, y, h:mm:ss a zzzz' (Monday, June 15, 2015 at 9:03:01 AM GMT+01:00).
5.      'shortDate': equivalent to 'M/d/yy' (6/15/15).
6.      'mediumDate': equivalent to 'MMM d, y' (Jun 15, 2015).
7.      'longDate': equivalent to 'MMMM d, y' (June 15, 2015).
8.      'fullDate': equivalent to 'EEEE, MMMM d, y' (Monday, June 15, 2015).
9.      'shortTime': equivalent to 'h:mm a' (9:03 AM).
10. 'mediumTime': equivalent to 'h:mm:ss a' (9:03:01 AM).
11. 'longTime': equivalent to 'h:mm:ss a z' (9:03:01 AM GMT+1).
12. 'fullTime': equivalent to 'h:mm:ss a zzzz' (9:03:01 AM GMT+01:00).
add datepipe in app.component.module.ts
import { BrowserModule } from '@angular/platform-browser';
import { NgModule } from '@angular/core';
import {DatePipe} from '@angular/common';
@NgModule({
  declarations: [
    AppComponent
  ],
  imports: [
    BrowserModule
  ],
  providers: [
    DatePipe
  ],
  bootstrap: [AppComponent]
})
export class AppModule { }