title: How to set fromDate in UNTimeIntervalNotificationTrigger
body: <p>I need to fire a notification at every 48 hours from a specific date. 
  I can schedule it using <code>UNTimeIntervalNotificationTrigger</code> as - </p>
  
  <pre><code>let trigger : UNTimeIntervalNotificationTrigger = UNTimeIntervalNotificationTrigger.init(timeInterval: TimeInterval(48 * 60 * 60), repeats: true);
  let content = UNMutableNotificationContent()   
     // Set the content whatever you want like title, subtitle, sound, userInfo 
  
  let request = UNNotificationRequest(identifier: alertId, content: content, trigger: trigger);
  </code></pre>
  
  <p>My problem is how to set the <code>fireDate</code>. I need to start this notification from a future date but using it, it is started from today.</p>
  
  <p>I also tried using <code>UNCalendarNotificationTrigger</code>(using component <code>[.hour, .minute]</code>) but it repeats every day as particular hour and minute matches every day. I also followed other solutions of stack overflow but still don't get any solution. </p>