Ionic3 error Unable to convert "[object Object]" into a date' for pipe 'DatePipe'?

Hello to all,
I have convert timestamp to date-format in ionic 3 and it is working properly initially load but after add new product and back to previous page above error is show i don’t understand why.i have tried with – (return new Date (timestamp) but not working same error occur?

<ion-list *ngFor="let catalog of allCatalog">  
       <span *ngIf="catalog.timestamp">{{catalog.timestamp | date}}</span>

Below our array param