docs: @Nonnull
    public static ICommonsSet <LocalDate> getIslamicHolidaysInGregorianYear (final int nGregorianYear,
                                                                             final int nIslamicMonth,
                                                                             final int nIslamicDay)
    {
      return getDatesFromChronologyWithinGregorianYear (nIslamicMonth,
                                                        nIslamicDay,
                                                        nGregorianYear,
                                                        HijrahChronology.INSTANCE);
    }