@Override
 public Object instantiateItem(ViewGroup container, int position) {
   WindFragment fragment = (WindFragment) super.instantiateItem(container, position);
   int day = Util.calculateDay(new Date()); // today
   mFragments.put(new Integer(position), fragment);
   return fragment;
 }
 @Override
 public Fragment getItem(int position) {
   WindFragment fragment = mFragments.get(new Integer(position));
   if (fragment == null) {
     int day = Util.calculateDay(new Date()); // today
     fragment = WindFragment.newInstance(mWindSpots.get(position % mWindSpots.size()), day);
     mFragments.put(new Integer(position), fragment);
   }
   return fragment;
 }