code: @Override
      public boolean isOn(Date date)
      {
          synchronized(calendar) {
              calendar.setTime(date);
              int dayOfYear = calendar.get(Calendar.DAY_OF_YEAR);
  
              calendar.setTime(computeInYear(calendar.getTime(), calendar));
  
              return calendar.get(Calendar.DAY_OF_YEAR) == dayOfYear;
          }
      }
docs: Return true if the given Date is on the same day as Easter