dateutil.pas

RX Library contains a large number of components, objects and routines for Borland Delphi with full

{*******************************************************}
{                                                       }
{         Delphi VCL Extensions (RX)                    }
{                                                       }
{         Copyright (c) 1995, 1996 AO ROSNO             }
{         Copyright (c) 1997, 1998 Master-Bank          }
{                                                       }
{*******************************************************}

unit DateUtil;

{$I RX.INC}
{$B-,V-,R-,Q-}

interface

  uses RTLConsts;

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 SysUtils, {$IFDEF WIN32} Windows, {$ENDIF} Consts, rxStrUtils;

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;