jvdateutil.pas

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{-----------------------------------------------------------------------------
The contents of this file are subject to the Mozilla Public License
Version 1.1 (the "License"); you may not use this file except in compliance
with the License. You may obtain a copy of the License at
http://www.mozilla.org/MPL/MPL-1.1.html

Software distributed under the License is distributed on an "AS IS" basis,
WITHOUT WARRANTY OF ANY KIND, either expressed or implied. See the License for
the specific language governing rights and limitations under the License.

The Original Code is: JvDateUtil.PAS, released on 2002-07-04.

The Initial Developers of the Original Code are: Fedor Koshevnikov, Igor Pavluk and Serge Korolev
Copyright (c) 1997, 1998 Fedor Koshevnikov, Igor Pavluk and Serge Korolev
Copyright (c) 2001,2002 SGB Software
All Rights Reserved.

Last Modified: 2002-07-04

You may retrieve the latest version of this file at the Project JEDI's JVCL home page,
located at http://jvcl.sourceforge.net

Known Issues:
-----------------------------------------------------------------------------}

{$I JVCL.INC}

unit JvDateUtil;

interface

{$IFDEF COMPILER6}
uses
  RTLConsts;
{$ELSE
{$IFDEF COMPILER7_UP}
uses
  SysConst;
{$ENDIF}

function CurrentYear: Word;
function IsLeapYear(AYear: Integer): Boolean;
function DaysPerMonth(AYear, AMonth: Integer): Integer;
function FirstDayOfPrevMonth: TDateTime;
function LastDayOfPrevMonth: TDateTime;
function FirstDayOfNextMonth: TDateTime;
function ExtractDay(ADate: TDateTime): Word;
function ExtractMonth(ADate: TDateTime): Word;
function ExtractYear(ADate: TDateTime): Word;
function IncDate(ADate: TDateTime; Days, Months, Years: Integer): TDateTime;
function IncDay(ADate: TDateTime; Delta: Integer): TDateTime;
function IncMonth(ADate: TDateTime; Delta: Integer): TDateTime;
function IncYear(ADate: TDateTime; Delta: Integer): TDateTime;
function ValidDate(ADate: TDateTime): Boolean;
procedure DateDiff(Date1, Date2: TDateTime; var Days, Months, Years: Word);
function MonthsBetween(Date1, Date2: TDateTime): Double;
function DaysInPeriod(Date1, Date2: TDateTime): Longint;
{ Count days between Date1 and Date2 + 1, so if Date1 = Date2 result = 1 }
function DaysBetween(Date1, Date2: TDateTime): Longint;
{ The same as previous but if Date2 < Date1 result = 0 }
function IncTime(ATime: TDateTime; Hours, Minutes, Seconds, MSecs: Integer): TDateTime;
function IncHour(ATime: TDateTime; Delta: Integer): TDateTime;
function IncMinute(ATime: TDateTime; Delta: Integer): TDateTime;
function IncSecond(ATime: TDateTime; Delta: Integer): TDateTime;
function IncMSec(ATime: TDateTime; Delta: Integer): TDateTime;
function CutTime(ADate: TDateTime): TDateTime; { Set time to 00:00:00:00 }

type
  TDateOrder = (doMDY, doDMY, doYMD);
  TDayOfWeekName = (Sun, Mon, Tue, Wed, Thu, Fri, Sat);
  TDaysOfWeek = set of TDayOfWeekName;

{ String to date conversions }
function GetDateOrder(const DateFormat: string): TDateOrder;
function MonthFromName(const S: string; MaxLen: Byte): Byte;
function StrToDateDef(const S: string; Default: TDateTime): TDateTime;
function StrToDateFmt(const DateFormat, S: string): TDateTime;
function StrToDateFmtDef(const DateFormat, S: string; Default: TDateTime): TDateTime;
function DefDateFormat(FourDigitYear: Boolean): string;
function DefDateMask(BlanksChar: Char; FourDigitYear: Boolean): string;

{$IFDEF WIN32}
function FormatLongDate(Value: TDateTime): string;
function FormatLongDateTime(Value: TDateTime): string;
{$ENDIF}

const
  DefaultDateOrder = doDMY;

{$IFDEF USE_FOUR_DIGIT_YEAR}
var
  FourDigitYear: Boolean;
{$ELSE}
function FourDigitYear: Boolean;
{$ENDIF USE_FOUR_DIGIT_YEAR}

const
  CenturyOffset: Byte = 60;
{$IFDEF WIN32}
  NullDate: TDateTime = {-693594} 0;
{$ELSE}
  NullDate: TDateTime = 0;
{$ENDIF}

implementation

uses
{$IFDEF WIN32}
  Windows,
{$ENDIF}
  SysUtils, Consts,
  JvStrUtils;

function IsLeapYear(AYear: Integer): Boolean;
begin
  Result := (AYear mod 4 = 0) and ((AYear mod 100 <> 0) or (AYear mod 400 = 0));
end;

function DaysPerMonth(AYear, AMonth: Integer): Integer;
const
  DaysInMonth: array[1..12] of Integer =
  (31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31);
begin
  Result := DaysInMonth[AMonth];
  if (AMonth = 2) and IsLeapYear(AYear) then
    Inc(Result); { leap-year Feb is special }
end;

function FirstDayOfNextMonth: TDateTime;
var
  Year, Month, Day: Word;
begin
  DecodeDate(Date, Year, Month, Day);
  Day := 1;
  if Month < 12 then
    Inc(Month)
  else
  begin
    Inc(Year);
    Month := 1;
  end;
  Result := EncodeDate(Year, Month, Day);
end;

function FirstDayOfPrevMonth: TDateTime;
var
  Year, Month, Day: Word;
begin
  DecodeDate(Date, Year, Month, Day);
  Day := 1;
  if Month > 1 then
    Dec(Month)
  else
  begin
    Dec(Year);
    Month := 12;
  end;
  Result := EncodeDate(Year, Month, Day);
end;

function LastDayOfPrevMonth: TDateTime;
var
  D: TDateTime;
  Year, Month, Day: Word;
begin
  D := FirstDayOfPrevMonth;
  DecodeDate(D, Year, Month, Day);
  Day := DaysPerMonth(Year, Month);
  Result := EncodeDate(Year, Month, Day);
end;

function ExtractDay(ADate: TDateTime): Word;
var
  M, Y: Word;
begin
  DecodeDate(ADate, Y, M, Result);
end;

function ExtractMonth(ADate: TDateTime): Word;
var
  D, Y: Word;
begin
  DecodeDate(ADate, Y, Result, D);
end;

function ExtractYear(ADate: TDateTime): Word;
var
  D, M: Word;
begin
  DecodeDate(ADate, Result, M, D);
end;

function IncDate(ADate: TDateTime; Days, Months, Years: Integer): TDateTime;
var
  D, M, Y: Word;
  Day, Month, Year: Longint;
begin
  DecodeDate(ADate, Y, M, D);
  Year := Y;
  Month := M;
  Day := D;
  Inc(Year, Years);
  Inc(Year, Months div 12);
  Inc(Month, Months mod 12);
  if Month < 1 then
  begin
    Inc(Month, 12);
    Dec(Year);
  end
  else if Month > 12 then
  begin
    Dec(Month, 12);
    Inc(Year);
  end;
  if Day > DaysPerMonth(Year, Month) then
    Day := DaysPerMonth(Year, Month);
  Result := EncodeDate(Year, Month, Day) + Days + Frac(ADate);
end;

procedure DateDiff(Date1, Date2: TDateTime; var Days, Months, Years: Word);
{ Corrected by Anatoly A. Sanko (2:450/73) }
var
  DtSwap: TDateTime;
  Day1, Day2, Month1, Month2, Year1, Year2: Word;
begin
  if Date1 > Date2 then
  begin
    DtSwap := Date1;
    Date1 := Date2;
    Date2 := DtSwap;
  end;
  DecodeDate(Date1, Year1, Month1, Day1);
  DecodeDate(Date2, Year2, Month2, Day2);
  Years := Year2 - Year1;
  Months := 0;
  Days := 0;
  if Month2 < Month1 then
  begin
    Inc(Months, 12);
    Dec(Years);
  end;
  Inc(Months, Month2 - Month1);
  if Day2 < Day1 then
  begin
    Inc(Days, DaysPerMonth(Year1, Month1));
    if Months = 0 then
    begin
      Dec(Years);
      Months := 11;
    end
    else
      Dec(Months);
  end;
  Inc(Days, Day2 - Day1);
end;

function IncDay(ADate: TDateTime; Delta: Integer): TDateTime;
begin
  Result := ADate + Delta;
end;

function IncMonth(ADate: TDateTime; Delta: Integer): TDateTime;
begin
  Result := IncDate(ADate, 0, Delta, 0);
end;

function IncYear(ADate: TDateTime; Delta: Integer): TDateTime;
begin
  Result := IncDate(ADate, 0, 0, Delta);
end;

function MonthsBetween(Date1, Date2: TDateTime): Double;
var
  D, M, Y: Word;
begin
  DateDiff(Date1, Date2, D, M, Y);
  Result := 12 * Y + M;
  if (D > 1) and (D < 7) then
    Result := Result + 0.25
  else if (D >= 7) and (D < 15) then
    Result := Result + 0.5
  else if (D >= 15) and (D < 21) then
    Result := Result + 0.75
  else if D >= 21 then
    Result := Result + 1;
end;

function IsValidDate(Y, M, D: Word): Boolean;
begin
  Result := (Y >= 1) and (Y <= 9999) and (M >= 1) and (M <= 12) and
    (D >= 1) and (D <= DaysPerMonth(Y, M));
end;

function ValidDate(ADate: TDateTime): Boolean;
var
  Year, Month, Day: Word;
begin
  try
    DecodeDate(ADate, Year, Month, Day);
    Result := IsValidDate(Year, Month, Day);
  except
    Result := False;
  end;
end;

function DaysInPeriod(Date1, Date2: TDateTime): Longint;
begin
  if ValidDate(Date1) and ValidDate(Date2) then
    Result := Abs(Trunc(Date2) - Trunc(Date1)) + 1
  else
    Result := 0;
end;

function DaysBetween(Date1, Date2: TDateTime): Longint;
begin
  Result := Trunc(Date2) - Trunc(Date1) + 1;
  if Result < 0 then
    Result := 0;
end;

function IncTime(ATime: TDateTime; Hours, Minutes, Seconds,
  MSecs: Integer): TDateTime;
begin
  Result := ATime + (Hours div 24) + (((Hours mod 24) * 3600000 +
    Minutes * 60000 + Seconds * 1000 + MSecs) / MSecsPerDay);
  if Result < 0 then
    Result := Result + 1;
end;

function IncHour(ATime: TDateTime; Delta: Integer): TDateTime;
begin
  Result := IncTime(ATime, Delta, 0, 0, 0);
end;

function IncMinute(ATime: TDateTime; Delta: Integer): TDateTime;
begin
  Result := IncTime(ATime, 0, Delta, 0, 0);
end;

function IncSecond(ATime: TDateTime; Delta: Integer): TDateTime;
begin
  Result := IncTime(ATime, 0, 0, Delta, 0);
end;

function IncMSec(ATime: TDateTime; Delta: Integer): TDateTime;
begin
  Result := IncTime(ATime, 0, 0, 0, Delta);
end;

function CutTime(ADate: TDateTime): TDateTime;
begin
  Result := Trunc(ADate);
end;

function CurrentYear: Word;
var
  SystemTime: TSystemTime;
begin
  GetLocalTime(SystemTime);
  Result := SystemTime.wYear;
end;

{ String to date conversions. Copied from SYSUTILS.PAS unit. }

procedure ScanBlanks(const S: string; var Pos: Integer);
var
  I: Integer;
begin
  I := Pos;
  while (I <= Length(S)) and (S[I] = ' ') do
    Inc(I);
  Pos := I;
end;

function ScanNumber(const S: string; MaxLength: Integer; var Pos: Integer;
  var Number: Longint): Boolean;
var
  I: Integer;
  N: Word;
begin
  Result := False;
  ScanBlanks(S, Pos);