Author: Christian Cristofori

I was trying to convert a DateTime value to a RFC822 style date, so I asked to 
Paolo, a friend of mine, if he did know how it works. He found that on the Net. 
It's not perfect... someone as a better one? 

Answer:
1   
2   function DateTimeToRFC822(DTTime: TDateTime): string;
3   var
4     IdX: Integer;
5     SaveShortDayNames: array[1..7] of string;
6     SaveShortMonthNames: array[1..12] of string;
7   const
8     MyShortDayNames: array[1..7] of string = ('Sun', 'Mon', 'Tue', 'Wed', 'Thu', 
9   'Fri',
10      'Sat');
11    MyShortMonthNames: array[1..12] of string = ('Jan', 'Feb', 'Mar', 'Apr', 'May',
12      'Jun', 'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec');
13  begin
14    if (ShortDayNames[1] = MyShortDayNames[1]) then
15      Result := FormatDateTime('ddd, d mmm yyyy hh:mm:ss', DTTime)
16    else
17    begin
18      for IdX := Low(ShortDayNames) to High(ShortDayNames) do
19      begin
20        SaveShortDayNames[IdX] := ShortDayNames[IdX];
21        ShortDayNames[IdX] := MyShortDayNames[IdX];
22      end;
23      for IdX := Low(ShortMonthNames) to High(ShortMonthNames) do
24      begin
25        SaveShortMonthNames[IdX] := ShortMonthNames[IdX];
26        ShortMonthNames[IdX] := MyShortMonthNames[IdX];
27      end;
28      Result := FormatDateTime('ddd, d mmm yyyy hh:mm:ss', DTTime);
29      for IdX := Low(ShortDayNames) to High(ShortDayNames) do
30        ShortDayNames[IdX] := SaveShortDayNames[IdX];
31      for IdX := Low(ShortMonthNames) to High(ShortMonthNames) do
32        ShortMonthNames[IdX] := SaveShortMonthNames[IdX];
33    end;
34  end;