Число текущей недели

function WeekOfYear(ADate: TDateTime): word;
var
  day: word;
  month: word;
  year: word;
  FirstOfYear: TDateTime;
begin
  DecodeDate(ADate, year, month, day);
  FirstOfYear := EncodeDate(year, 1, 1);
  Result := Trunc(ADate - FirstOfYear) div 7 + 1;
end;
 
procedure TForm1.Button1Click(Sender: TObject);
begin
  ShowMessage(IntToStr(WeekOfYear(Date)));
end;
 

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DelphiWorld 6.0

function WeekNum(const ADate: TDateTime): word;
var
  Year: word;
  Month: word;
  Day: word;
begin
  DecodeDate(ADate + 4 - DayOfWeek(ADate + 6), Year, Month, Day);
  result := 1 + trunc((ADate - EncodeDate(Year, 1, 5) +
    DayOfWeek(EncodeDate(Year, 1, 3))) / 7);
end;

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DelphiWorld 6.0

function WeekOfYear(Dat: TDateTime): Word;
// Интерпретация номеров дней:
// ISO: 1 = Понедельник, 7 = Воскресенье
// Delphi SysUtils: 1 = Воскресенье, 7 = Суббота
var
  Day, Month, Year: Word;
  FirstDate: TDateTime;
  DateDiff: Integer;
begin
  day := SysUtils.DayOfWeek(Dat) - 1;
  Dat := Dat + 3 - ((6 + day) mod 7);
  DecodeDate(Dat, Year, Month, Day);
  FirstDate := EncodeDate(Year, 1, 1);
  DateDiff := Trunc(Dat - FirstDate);
  Result := 1 + (DateDiff div 7);
end;

https://delphiworld.narod.ru/

DelphiWorld 6.0