How to check if a built-in iOS app is deleted?

I'm trying to detect built-in iOS apps (Calendar, Reminders, Weather) exist or not.

I've tried using canOpenURL:.

- (BOOL) isCalendarExist {
  UIApplication *app = [UIApplication sharedApplication];  
  NSURL *calUrl= [NSURL URLWithString: @"calshow://"];
  return [app canOpenURL: calUrl];
}

But canOpenURL: always return TRUE value even if Calendar is deleted.

Is there anyway to check if a built-in app exists or not?