title: Ionic how to fix "ExpressionChangedAfterItHasBeenCheckedError" error?
body: <p>//html</p>
  
  <pre><code>    &lt;span style="margin-left:43%;background-color:rgb(229,229,229);border-
      radius:10%"&gt;&amp;nbsp;&amp;nbsp;{{formatEpoch(epoch)}}&amp;nbsp;&amp;nbsp;&lt;/span&gt;
  </code></pre>
  
  <p>//ts</p>
  
  <pre><code>lastdate:any;                    
  
   formatEpoch(epoch): string {
      if(epoch == this.lastdate){
          return '';
      }else{ 
      this.lastdate =epoch;
      return UtilService.getCalendarDay(epoch);
      }
    }
  </code></pre>
  
  <p>ExpressionChangedAfterItHasBeenCheckedError: Expression has changed after it was checked. Previous value: '今天 5:34 PM'. Current value: ''.</p>
  
  <p>How can i fix this error? Please help.</p>