I am asking for an input of type "date" and then I want to use the received dates stored in variables. I am receiving the user input correctly but the I don't know what type of data to use with JavaSript, currently I'm receiving it as "number" but it's not appropriate.
    <form #datesForm = "ngForm" (ngSubmit)="checkDates(datesForm.value)">
    <div class="elem-group inlined">
      <label>First Day Of Your Plan</label>
      <input type="date" name="firstDate" required>
    </div>
    <div class="elem-group inlined">
      <label>Last Day Of Your Plan</label>
      <input type="date" name="lastDate" required>
    </div>
    <button class="btn-fetch" (click)="checkDates(datesForm.value)">Confirm Dates</button>
    <div class="elem-group">
      <label>Select A Plan Number </label>
      <select name="planId" required>
          <option value="">Choose a number from the List</option>
          <option value="planId">Connecting</option>
      </select>
    </div>
    <button type="submit">Save the Plan</button>
</form>
export class PlansComponent {
  @ViewChild('plansForm') form: NgForm;
  checkDates(planDates: { firstDate: number, lastDate: number }) {
    if (planDates.lastDate - planDates.firstDate <= 7)
      confirm("Dates are OK");
    else
      alert("Only weekly dates");
  }
What would you have me use instead of number in my checkDates() method?