Iondatetime...not applying date to ngModel

<ion-datetime  style="display:none"
          #datePicker4 (ionChange)="timeselect2()"
          displayFormat="M/D a:hh:mm"
          pickerFormat="M/D a:hh:mm"
          [(ngModel)]="deathdate">
          </ion-datetime>


when I clicked it , it shows Month date, hour,minutes well
but the problem is that when I set specific date,
it comes to timeselect2 function which log deathdate.
but deathdate value only show hour and month…

why is it?