Преобразовать Персидскую дату в дату по Грегорианскому календарю

function Persia_to_Ger_date(aa: ShortString; ResultKind: Byte = 0): ShortString;
 
   function TrueTo1(co: Boolean): Integer;
   begin
     if co then TrueTo1 := 1
      else
        TrueTo1 := 0;
   end;
 
    const
   Conm_mons: array[0..11] of Byte = (31,28,31,30,31,30,31,31,30,31,30,31);
   LeapYearSh: array[0..4] of Integer = (1375,1379,1383,1387,1391);
   LeapYearMi: array[0..4] of Integer = (1996,2000,2004,2008,2012);
   monthes: array[0..11] of ShortString = ('Jan', 'Feb', 'Mar', 'Apr',
     'May', 'Jun', 'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec');
 type
   date = record
     da_day, da_mon, da_year: Integer;
   end;
 var
   m_mons: array[0..11] of BYTE;
   LastDayCountSh, LastDayCountMi: integer;
   a, b: date;
   sYY, sMM, sDD: ShortString;
   I: Integer;
 begin
   for I := Low(Conm_mons) to High(Conm_mons) do
     m_mons[I] := Conm_mons[I];
 
   a.da_day  := StrToNum(Copy(aa, DayPosInDate, DayLen));
   a.da_mon  := StrToNum(Copy(aa, MonthPosInDate, MonthLen));
   a.da_year := StrToNum(Copy(aa, YearPosInDate, YearLen));
   b.da_year := a.da_year + 621;
   Inc(b.da_year, TrueTo1(((a.da_mon > 10) or ((a.da_mon = 10) and (a.da_day >= 12)))
     or ((LeapYearSh[(a.da_year - 1374) div 4] <> a.da_year) and
     ((a.da_mon = 10) and (a.da_day = 11)))));
   Inc(m_mons[1], TrueTo1(LeapYearMi[(b.da_year - 1996) div 4] = b.da_year));
   if (a.da_mon <= 7) then LastDayCountSh := ((a.da_mon - 1) * 31 + a.da_day)
   else
      LastDayCountSh := (186 + (a.da_mon - 7) * 30 + a.da_day);
   if (b.da_year = (a.da_year + 622)) then LastDayCountMi :=
       LastDayCountSh - 286 - TrueTo1(LeapYearSh[(a.da_year - 1375) div 4] = a.da_year)
   else
      LastDayCountMi := (LastDayCountSh + 79);
 
   b.da_day := LastDayCountMi;
   b.da_mon := 0;
   while (LastDayCountMi > m_mons[b.da_mon]) do
   begin
     Dec(LastDayCountMi, m_mons[b.da_mon]);
     Inc(b.da_mon);
     b.da_day := LastDayCountMi;
   end;
   Inc(b.da_mon);
   if b.da_year < 1000 then sYY := sYY + '0';
   if b.da_year < 100 then sYY := sYY + '0';
   if b.da_year < 10 then sYY := sYY + '0';
   sYY := sYY + IntToStr(b.da_year);
 
   if b.da_mon < 10 then sMM := sMM + '0';
   sMM := sMM + IntToStr(b.da_mon);
 
   if b.da_day < 10 then sDD := sDD + '0';
   sDD := sDD + IntToStr(b.da_day);
 
   case ResultKind of
     0: Persia_to_Ger_date := sYY + '/' + sMM + '/' + sDD;
     1: Persia_to_Ger_date := sYY + ' ' + monthes[b.da_mon - 1] + ' ' + sDD;
   end;
 end;

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