Тъп въпрос !

unit EGNCheck;



interface

const EGN_Mod_11_Coef : array[1..9] of byte = (2,4,8,5,10,9,7,3,6);



type EGNString = string[10];

  {Проверява ЕГН}

  function CheckEGN(EGN : EGNString) : boolean;

  {}

  function CheckEGN_Mod11(EGN : EGNString) : boolean;

  {}

  function CheckEGN_Date(EGN : EGNString) : boolean;



  {Взема дата от ЕГН}

  function GetDateFromEGN(EGN : EGNString) : TDateTime;



  {Проверява дали годината е високосна}

  function LeapYear(Year : word) : boolean;



  {Образува ЕГН от подадена дата, като последните 4 символа са нули}

  function DateToEGNwith0(Date : TDateTime): string;



implementation



uses SysUtils;



function DateToEGNwith0(Date : TDateTime): string;

var Y,M,D : word;

    S : string[10];

begin

  DecodeDate(Date,Y,M,D);

  if (Y >=1800) and (Y<=1899) then

    M := M + 20;

  if (Y >=1900) and (Y<=1999) then M := M + 0;

  if (Y >=2000) then M := M + 40;

  Result := Copy(IntToStr(Y),3,2);



  S := IntToStr(M);

  if Length(S) = 1 then S := '0' + S;

  Result := Result + S;



  S := IntToStr(D);

  if Length(S) = 1 then S := '0' + S;

  Result := Result + S + '0000';

end;



function GetDateFromEGN(EGN : EGNString) : TDateTime;

var Y,M,D : word;

begin

  Y := StrToInt(Copy(EGN,1,2));

  M := StrToInt(Copy(EGN,3,2));

  D := StrToInt(Copy(EGN,5,2));

  if M > 20 then

  begin

    if M > 40 then begin

      M := M - 40;

      Y := Y + 2000;

    end

    else begin

      M := M - 20;

      Y := Y + 1800;

    end

  end

  else Y := Y + 1900;



  try

    Result := EncodeDate(Y,M,D);

  except

    on EConvertError do

    begin

      Result := 0;

    end;

  end;



end;



function LeapYear(Year : word) : boolean;

begin

  if (Year mod 4 <> 0) then

    Result := False

  else if (Year mod 100 <> 0) then

     Result := true

  else if (Year mod 400 <> 0) then

     Result := False

  else Result := True;



end;



function CheckEGN_Date(EGN : EGNString) : boolean;

var Y,M,D : word;

begin

  Y := StrToInt(Copy(EGN,1,2));

  M := StrToInt(Copy(EGN,3,2));

  D := StrToInt(Copy(EGN,5,2));

  if M > 20 then

  begin

    if M > 40 then begin

      M := M - 40;

      Y := Y + 2000;

    end

    else begin

      M := M - 20;

      Y := Y + 1800;

    end

  end

  else Y := Y + 1900;



  Result := True;

  try

    EncodeDate(Y,M,D);

  except

    on EConvertError do

    begin

      Result := False;

    end;

  end;

end;



function CheckEGN_Mod11(EGN : EGNString) : boolean;

var i,M : integer;

begin

  if EGN[0] < #10 then

  begin

    Result := False;

    exit;

  end;

  M := 0;

  for i := 1 to 9 do

  begin

    M := M + StrToInt(EGN)*EGN_Mod_11_Coef;

  end;

  M := (M mod 11) mod 10;

  Result := StrToInt(EGN[10]) = M;

end;





function CheckEGN(EGN : EGNString) : boolean;

begin

  Result := CheckEGN_Mod11(EGN) and CheckEGN_Date(EGN);

end;



end.