dateutils.pp

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          (ADayOfYear<=DaysPerYear[IsLeapYear(AYear)]);
end;


Function IsValidDateWeek(const AYear, AWeekOfYear, ADayOfWeek: Word): Boolean;
begin
  Result:=(AYear<>0) and (AYear<10000)
          and (ADayOfWeek in [1..7])
          and (AWeekOfYear<>0)
          and (AWeekOfYear<=WeeksInaYear(AYear));
  { should we not also check whether the day of the week is not
    larger than the last day of the last week in the year 9999 ?? }
end;


Function IsValidDateMonthWeek(const AYear, AMonth, AWeekOfMonth, ADayOfWeek: Word): Boolean;

begin
  Result:=(AYear<>0) and (AYear<10000)
          and (AMonth in [1..12])
          and (AWeekOfMonth in [1..5])
          and (ADayOfWeek in [1..7]);
end;

{ ---------------------------------------------------------------------
    Enumeration functions.
  ---------------------------------------------------------------------}

Function WeeksInYear(const AValue: TDateTime): Word;

Var
  Y,M,D : Word;

begin
  DecodeDate(AValue,Y,M,D);
  Result:=WeeksInAYear(Y);
end;


Function WeeksInAYear(const AYear: Word): Word;

Var
  DOW : Word;

begin
  Result:=52;
  DOW:=DayOfTheWeek(StartOfAYear(AYear));
  If (DOW=4) or ((DOW=3) and IsLeapYear(AYear)) then
    Inc(Result);
end;


Function DaysInYear(const AValue: TDateTime): Word;

Var
  Y,M,D : Word;

begin
  DecodeDate(AValue,Y,M,D);
  Result:=DaysPerYear[IsLeapYear(Y)];
end;


Function DaysInAYear(const AYear: Word): Word;
begin
  Result:=DaysPerYear[Isleapyear(AYear)];
end;


Function DaysInMonth(const AValue: TDateTime): Word;

Var
  Y,M,D : Word;

begin
  Decodedate(AValue,Y,M,D);
  Result:=MonthDays[IsLeapYear(Y),M];
end;


Function DaysInAMonth(const AYear, AMonth: Word): Word;
begin
  Result:=MonthDays[IsLeapYear(AYear),AMonth];
end;


{ ---------------------------------------------------------------------
    Variations on current date/time.
  ---------------------------------------------------------------------}


Function Today: TDateTime;
begin
  Result:=Date;
end;


Function Yesterday: TDateTime;
begin
  Result:=Date-1;
end;


Function Tomorrow: TDateTime;
begin
  Result:=Date+1;
end;


Function IsToday(const AValue: TDateTime): Boolean;
begin
  Result:=IsSameDay(AValue,Date);
end;


Function IsSameDay(const AValue, ABasis: TDateTime): Boolean;

Var
  D : TDateTime;

begin
  D:=AValue-Trunc(ABasis);
  Result:=(D>=0) and (D<1);
end;

const
  DOWMap: array [1..7] of Word = (7, 1, 2, 3, 4, 5, 6);

Function PreviousDayOfWeek (DayOfWeek : Word) : Word;

begin
  If Not (DayOfWeek in [1..7]) then
    Raise EConvertError.CreateFmt(SErrInvalidDayOfWeek,[DayOfWeek]);
  Result:=DOWMap[DayOfWeek];
end;



{ ---------------------------------------------------------------------
    Extraction functions.
  ---------------------------------------------------------------------}


Function YearOf(const AValue: TDateTime): Word;

Var
  D,M : Word;

begin
  DecodeDate(AValue,Result,D,M);
end;


Function MonthOf(const AValue: TDateTime): Word;

Var
  Y,D : Word;

begin
  DecodeDate(AValue,Y,Result,D);
end;


Function WeekOf(const AValue: TDateTime): Word;
begin
  Result:=WeekOfTheYear(AValue);
end;


Function DayOf(const AValue: TDateTime): Word;

Var
  Y,M : Word;

begin
  DecodeDate(AValue,Y,M,Result);
end;


Function HourOf(const AValue: TDateTime): Word;

Var
  N,S,MS : Word;

begin
  DecodeTime(AValue,Result,N,S,MS);
end;


Function MinuteOf(const AValue: TDateTime): Word;

Var
  H,S,MS : Word;

begin
  DecodeTime(AValue,H,Result,S,MS);
end;


Function SecondOf(const AValue: TDateTime): Word;

Var
  H,N,MS : Word;

begin
  DecodeTime(AVAlue,H,N,Result,MS);
end;


Function MilliSecondOf(const AValue: TDateTime): Word;

Var
  H,N,S : Word;

begin
  DecodeTime(AValue,H,N,S,Result);
end;


{ ---------------------------------------------------------------------
    Start/End of year functions.
  ---------------------------------------------------------------------}


Function StartOfTheYear(const AValue: TDateTime): TDateTime;

Var
  Y,M,D : Word;

begin
  DecodeDate(AValue,Y,M,D);
  Result:=EncodeDate(Y,1,1);
end;


Function EndOfTheYear(const AValue: TDateTime): TDateTime;

Var
  Y,M,D : Word;

begin
  DecodeDate(AValue,Y,M,D);
  Result:=EncodeDateTime(Y,12,31,23,59,59,999);
end;


Function StartOfAYear(const AYear: Word): TDateTime;
begin
  Result:=EncodeDate(AYear,1,1);
end;


Function EndOfAYear(const AYear: Word): TDateTime;

begin
  Result:=(EncodeDateTime(AYear,12,31,23,59,59,999));
end;

{ ---------------------------------------------------------------------
    Start/End of month functions.
  ---------------------------------------------------------------------}

Function StartOfTheMonth(const AValue: TDateTime): TDateTime;

Var
  Y,M,D : Word;

begin
  DecodeDate(AValue,Y,M,D);
  Result:=EncodeDate(Y,M,1);
//  MonthDays[IsLeapYear(Y),M])
end;


Function EndOfTheMonth(const AValue: TDateTime): TDateTime;

Var
  Y,M,D : Word;

begin
  DecodeDate(AValue,Y,M,D);
  Result:=EncodeDateTime(Y,M,MonthDays[IsLeapYear(Y),M],23,59,59,999);
end;


Function StartOfAMonth(const AYear, AMonth: Word): TDateTime;
begin
  Result:=EncodeDate(AYear,AMonth,1);
end;


Function EndOfAMonth(const AYear, AMonth: Word): TDateTime;

begin
  Result:=EncodeDateTime(AYear,AMonth,MonthDays[IsLeapYear(AYear),AMonth],23,59,59,999);
end;


{ ---------------------------------------------------------------------
    Start/End of week functions.
  ---------------------------------------------------------------------}


Function StartOfTheWeek(const AValue: TDateTime): TDateTime;
begin
  Result:=Trunc(AValue)-DayOfTheWeek(AValue)+1;
end;


Function EndOfTheWeek(const AValue: TDateTime): TDateTime;
begin
  Result:=EndOfTheDay(AValue-DayOfTheWeek(AValue)+7);
end;


Function StartOfAWeek(const AYear, AWeekOfYear: Word; const ADayOfWeek: Word): TDateTime;
begin
  Result:=EncodeDateWeek(AYear,AWeekOfYear,ADayOfWeek);
end;


Function StartOfAWeek(const AYear, AWeekOfYear: Word): TDateTime; // ADayOFWeek 1
begin
  Result:=StartOfAWeek(AYear,AWeekOfYear,1)
end;


Function EndOfAWeek(const AYear, AWeekOfYear: Word; const ADayOfWeek: Word): TDateTime;
begin
  Result := EndOfTheDay(EncodeDateWeek(AYear, AWeekOfYear, ADayOfWeek));
end;


Function EndOfAWeek(const AYear, AWeekOfYear: Word): TDateTime; // const ADayOfWeek: Word = 7


begin
  Result:=EndOfAWeek(AYear,AWeekOfYear,7);
end;

{ ---------------------------------------------------------------------
    Start/End of day functions.
  ---------------------------------------------------------------------}

Function StartOfTheDay(const AValue: TDateTime): TDateTime;
begin
  StartOfTheDay:=Trunc(Avalue);
end;


Function EndOfTheDay(const AValue: TDateTime): TDateTime;

Var
  Y,M,D : Word;

begin
  DecodeDate(AValue,Y,M,D);
  Result:=EncodeDateTime(Y,M,D,23,59,59,999);
end;


Function StartOfADay(const AYear, AMonth, ADay: Word): TDateTime;
begin
  Result:=EncodeDate(AYear,AMonth,ADay);
end;


Function StartOfADay(const AYear, ADayOfYear: Word): TDateTime;
begin
  Result:=StartOfAYear(AYear)+ADayOfYear;
end;


Function EndOfADay(const AYear, AMonth, ADay: Word): TDateTime;
begin
  Result:=EndOfTheDay(EncodeDate(AYear,AMonth,ADay));
end;


Function EndOfADay(const AYear, ADayOfYear: Word): TDateTime;


begin
  Result:=StartOfAYear(AYear)+ADayOfYear+EncodeTime(23,59,59,999);
end;

{ ---------------------------------------------------------------------
    Part of year functions.
  ---------------------------------------------------------------------}


Function MonthOfTheYear(const AValue: TDateTime): Word;

Var
  Y,D : Word;

begin
  DecodeDate(AValue,Y,Result,D);
end;


Function WeekOfTheYear(const AValue: TDateTime): Word;

Var
  Y,DOW : Word;

begin
  DecodeDateWeek(AValue,Y,Result,DOW)
end;


Function WeekOfTheYear(const AValue: TDateTime; var AYear: Word): Word;

Var
  DOW : Word;

begin
  DecodeDateWeek(AValue,AYear,Result,DOW);
end;


Function DayOfTheYear(const AValue: TDateTime): Word;
begin
  Result:=Trunc(AValue-StartOfTheYear(AValue)+1);
end;


Function HourOfTheYear(const AValue: TDateTime): Word;

Var
  H,M,S,MS : Word;

begin
  DecodeTime(AValue,H,M,S,MS);
  Result:=H+((DayOfTheYear(AValue)-1)*24);
end;


Function MinuteOfTheYear(const AValue: TDateTime): LongWord;

Var
  H,M,S,MS : Word;

begin
  DecodeTime(AValue,H,M,S,MS);
  Result:=M+(H+((DayOfTheYear(AValue)-1)*24))*60;
end;


Function SecondOfTheYear(const AValue: TDateTime): LongWord;

Var
  H,M,S,MS : Word;

begin
  DecodeTime(AValue,H,M,S,MS);
  Result:=(M+(H+((DayOfTheYear(AValue)-1)*24))*60)*60+S;
end;


Function MilliSecondOfTheYear(const AValue: TDateTime): Int64;

Var
  H,M,S,MS : Word;

begin
  DecodeTime(AValue,H,M,S,MS);
  Result:=((M+(H+((DayOfTheYear(AValue)-1)*24))*60)*60+S)*1000+MS;
end;


{ ---------------------------------------------------------------------
    Part of month functions.
  ---------------------------------------------------------------------}


Function WeekOfTheMonth(const AValue: TDateTime): Word;

var
  Y,M,DOW : word;

begin
  DecodeDateMonthWeek(AValue,Y,M,Result,DOW);
end;


Function WeekOfTheMonth(const AValue: TDateTime; var AYear, AMonth: Word): Word;

Var
  DOW : Word;

begin
  DecodeDateMonthWeek(AValue,AYear,AMonth,Result,DOW);