How to change model structure of angular powered bootstrap ngbDatepicker

So I think the easiest way to solve your problem is to provide your own implementation of NgbDateAdapter and inject that into you component. You will need to add

{provide: NgbDateAdapter, useClass: NgbUTCStringAdapter}

to you components providers array and define the NgbUTCStringAdapter somewhere:

@Injectable()export class NgbUTCStringAdapter extends NgbDateAdapter<string> {  fromModel(date: string): NgbDateStruct {    return (date && Number(date.substring(0, 4)) && Number(date.substring(5, 7) + 1) && Number(date.substring(8, 10))) ?                {year: Number(date.substring(0, 4)),                    month: Number(date.substring(5, 7)),                    day: Number(date.substring(8, 10))} : null;  }  toModel(date: NgbDateStruct): string {    return date ? date.year.toString() + '-' + String('00' + date.month).slice(-2)                            + '-' + String('00' + date.day).slice(-2) : null;  }}

The other way to do it would be to put this code into your custom form control something like this:

@Component({selector: 'app-date',templateUrl: './date.component.html',providers: [    {        provide: NG_VALUE_ACCESSOR,        useExisting: forwardRef(() => DateComponent),        multi: true    },    {provide: NgbDateParserFormatter, useClass: NgbDateOmniParserFormatter}]})export class DateComponent implements ControlValueAccessor {  model;  writeValue(value: any) {    this.model =  (value && Number(value.substring(0, 4)) &&                         Number(value.substring(5, 7) + 1) &&                        Number(value.substring(8, 10))) ?                            {year: Number(value.substring(0, 4)),                             month: Number(value.substring(5, 7)),                             day: Number(value.substring(8, 10))} : null;  }  propagateChange = (_: any) => {};  registerOnChange(fn) {    this.propagateChange = fn;  }  registerOnTouched() {}  change() {    const date = this.model ? this.model.year.toString() + '-' +                    String('00' + this.model.month).slice(-2) + '-' +                   String('00' + this.model.day).slice(-2) : null;    this.propagateChange(date);  }}