title: PrimeNG calendar is not working as expected in Angular5
body: <p>I am using PrimeNG calendar for date of birth field. I am using <code>yearNavigator</code> and <code>yearRange</code>. The user can select max value is 12 years back before the current year.</p>
  
  <pre><code>&lt;p-calendar formControlName="dob" class="" id="dob-registration" dateFormat="dd/mm/yy" placeholder="DD/MM/YYYY"
            readonlyInput="true" [monthNavigator]="true" [yearNavigator]="true" [yearRange]="dobYearRange" [maxDate]="maxYearDate"&gt;&lt;/p-calendar&gt;
  </code></pre>
  
  <p>So I am assigning the values like</p>
  
  <pre><code>this.maxYearDate = new Date(new Date().setFullYear(new Date().getFullYear() - 12));
  this.dobYearRange = '1900:' + (new Date().getFullYear() -12);
  </code></pre>
  
  <p>Now the year and month is coming from a dropdown as expected. But the problem is initially year dropdown's initial value is 1900 and showing current date all disabled status. </p>
  
  <p>How can I set year drop down value is 12 years back and date exactly 12 years back ?</p>