code: @Nonnull
    public static ICommonsSet <LocalDate> getIslamicHolidaysInGregorianYear (final int nGregorianYear,
                                                                             final int nIslamicMonth,
                                                                             final int nIslamicDay)
    {
      return getDatesFromChronologyWithinGregorianYear (nIslamicMonth,
                                                        nIslamicDay,
                                                        nGregorianYear,
                                                        HijrahChronology.INSTANCE);
    }
docs: Returns a set of gregorian dates within a gregorian year which equal the
  islamic month and day. Because the islamic year is about 11 days shorter
  than the gregorian there may be more than one occurrence of an islamic date
  in an gregorian year. i.e.: In the gregorian year 2008 there were two 1/1.
  They occurred on 1/10 and 12/29.
  
  @param nGregorianYear
  Year to convert
  @param nIslamicMonth
  Month to convert
  @param nIslamicDay
  Day to convert
  @return List of gregorian dates for the islamic month/day.