Filtering PrimeNg Table with custom Date filter throwing error saying value is undefined

Question

I have PrimeNg Table where I show some data, including dates, here's the relevant part of .html:

<p-table
      #dt
      [columns]="subjectsColls"
      [value]="relatedSubjects"
    >
      <ng-template pTemplate="header" let-columns>
        <tr>
          <!-- Here column headers are defined -->
        </tr>
        <tr>
          <ng-container *ngFor="let col of columns" [ngSwitch]="col.field">
            <th *ngSwitchCase="'validFrom'">
               <p-calendar
                      [(ngModel)]="dt['filters']['validFrom'] && dt['filters'][col.field].value"
                      (onSelect)="dt.filter($event, col.field, 'dateFilter')"
                      (onClearClick)="dt.filter(null, col.field, 'dateFilter')"
                      (onTodayClick)="dt.filter(currentDate, col.field, 'dateFilter')"
                      [style]="{ width: '100%' }"
                      dateFormat="yy-mm-dd"
                      showButtonBar="true"
                      [appendTo]="'body'"
                ></p-calendar>
           </th>
         </ng-container>
       </tr>
     </ng-template>
     <!-- Here table body is defined -->
</p-table>

Here is my .ts component with custom filter in ngOnInit:

@Component({...})
export class MyComponent implements OnInit {
@ViewChild('dt', {static: false}) public _table: Table;

 ngOnInit() {
 FilterUtils['dateFilter'] = (value, filter): boolean => {
      console.log(value); // return null and I don't know why
      return value.getTime() === filter.getTime();
    };
 }
}

But if I try to filter with any selected date in calendar an error pops up in console:

ERROR TypeError: Cannot read property 'getTime' of undefined
    at primeng_primeng__WEBPACK_IMPORTED_MODULE_5__.FilterUtils.dateFilter

Why does value return null in ngOnInit FilterUtils?