<div (click)="onItemClick()"
     [ngClass]="{ 'work__day': 'true'}">
    {{myDate.getDate()}}
</div>

export class MyItemComponent{
    @Input() myDate: Date;    
    @Output() onClick: EventEmitter<Date> = new EventEmitter();

    ngOnInit(): void {        
    }

    private onItemClick ()
    {        
        this.onClick.emit(this.myDate);
    }
}

<div class="mycalendar" >
   <my-item *ngFor="let date of dates" [myDate]="date" (onClick)="onDateClick($event)"></my-item>
</div>

<my-item ng-reflect-item="[object Object]" >
	<div ng-reflect-ng-class="[object Object]" class="work__day">
    6
	</div>
</my-item>

<div class="mycalendar" >
   <my-item *ngFor="let date of dates" [myDate]="date" (onClick)="onDateClick($event)" [ngClass]="{ 'work__day': 'true'}"></my-item>
</div>

@Directive({
  (...)
  host: {
    '[class.className]' : 'className', 
    '[class]' : 'classNames' 
  }
}
export class MyDirective {
  constructor() {
    this.className = true;
    this.classNames = 'class1 class2 class3';
  }
}