Project Structure

• NewDate.dpr
• DateF.pas
• Dates.pas
• DateF.dfm

program NewDate;

uses
  Forms,
  DateF in 'DateF.pas' {DateForm},
  Dates in 'Dates.pas';

{$R *.RES}

begin
  Application.Initialize;
  Application.CreateForm(TDateForm, DateForm);
  Application.Run;
end.

unit DateF;

interface

uses
  SysUtils, Windows, Messages, Classes, Graphics, Controls,
  Forms, Dialogs, Dates, StdCtrls;

type
  TDateForm = class(TForm)
    LabelDate: TLabel;
    BtnIncrease: TButton;
    BtnDecrease: TButton;
    BtnAdd10: TButton;
    BtnSubtract10: TButton;
    BtnLeap: TButton;
    BtnToday: TButton;
    procedure BtnIncreaseClick(Sender: TObject);
    procedure FormCreate(Sender: TObject);
    procedure BtnDecreaseClick(Sender: TObject);
    procedure BtnAdd10Click(Sender: TObject);
    procedure BtnSubtract10Click(Sender: TObject);
    procedure FormDestroy(Sender: TObject);
    procedure BtnLeapClick(Sender: TObject);
    procedure BtnTodayClick(Sender: TObject);
  private
    TheDay: TNewDate;
  public
    { Public declarations }
  end;

var
  DateForm: TDateForm;

implementation

{$R *.DFM}

procedure TDateForm.FormCreate(Sender: TObject);
begin
  TheDay := TNewDate.Create (2001, 12, 25);
  LabelDate.Caption := TheDay.GetText;
end;

procedure TDateForm.BtnIncreaseClick(Sender: TObject);
begin
  TheDay.Increase;
  LabelDate.Caption := TheDay.GetText;
end;

procedure TDateForm.BtnDecreaseClick(Sender: TObject);
begin
  TheDay.Decrease;
  LabelDate.Caption := TheDay.GetText;
end;

procedure TDateForm.BtnAdd10Click(Sender: TObject);
begin
  TheDay.Increase (10);
  LabelDate.Caption := TheDay.GetText;
end;

procedure TDateForm.BtnSubtract10Click(Sender: TObject);
begin
  TheDay.Decrease (10);
  LabelDate.Caption := TheDay.GetText;
end;

procedure TDateForm.FormDestroy(Sender: TObject);
begin
  TheDay.Free;
end;

procedure TDateForm.BtnLeapClick(Sender: TObject);
begin
  if TheDay.LeapYear then
    ShowMessage ('Leap year')
  else
    ShowMessage ('NON Leap year');
end;

procedure TDateForm.BtnTodayClick(Sender: TObject);
begin
  TheDay.SetValue (Date);
  LabelDate.Caption := TheDay.GetText;
end;

end.

unit Dates;

interface

type
  TDate = class
  private
    fDate: TDateTime;
    procedure SetDay(const Value: Integer);
    procedure SetMonth(const Value: Integer);
    procedure SetYear(const Value: Integer);
    function GetDay: Integer;
    function GetMonth: Integer;
    function GetYear: Integer;
  public
    constructor Create; overload;
    constructor Create (y, m, d: Integer); overload;
    procedure SetValue (y, m, d: Integer); overload;
    procedure SetValue (NewDate: TDateTime); overload;
    procedure Assign(Source: TDate);

    function LeapYear: Boolean;
    procedure Increase (NumberOfDays: Integer = 1);
    procedure Decrease (NumberOfDays: Integer = 1);
    function GetText: string;

    property Year: Integer read GetYear write SetYear;
    property Month: Integer read GetMonth write SetMonth;
    property Day: Integer read GetDay write SetDay;
  end;

  TNewDate = class (TDate)
  public
     function GetText: string;
  end;

implementation

uses
  SysUtils, DateUtils;

procedure TDate.Assign (Source: TDate);
begin
  fDate := Source.fDate;
end;

procedure TDate.SetValue (y, m, d: Integer);
begin
  fDate := EncodeDate (y, m, d);
end;

function TDate.LeapYear: Boolean;
begin
  Result := IsInLeapYear(fDate);
end;

procedure TDate.Increase (NumberOfDays: Integer = 1);
begin
  fDate := fDate + NumberOfDays;
end;

function TDate.GetText: string;
begin
  GetText := DateToStr (fDate);
end;

procedure TDate.Decrease (NumberOfDays: Integer = 1);
begin
  fDate := fDate - NumberOfDays;
end;

constructor TDate.Create (y, m, d: Integer);
begin
  fDate := EncodeDate (y, m, d);
end;

constructor TDate.Create;
begin
  fDate := Date;
end;

procedure TDate.SetValue(NewDate: TDateTime);
begin
  fDate := NewDate;
end;

procedure TDate.SetDay(const Value: Integer);
begin
  fDate := RecodeDay (fDate, Value);
end;

procedure TDate.SetMonth(const Value: Integer);
begin
  fDate := RecodeMonth (fDate, Value);
end;

procedure TDate.SetYear(const Value: Integer);
begin
  fDate := RecodeYear (fDate, Value);
end;

function TDate.GetDay: Integer;
begin
  Result := DayOf (fDate);
end;

function TDate.GetMonth: Integer;
begin
  Result := MonthOf (fDate);
end;

function TDate.GetYear: Integer;
begin
  Result := YearOf (fDate);
end;

{ TNewDate }

function TNewDate.GetText: string;
begin
  GetText := FormatDateTime ('dddddd', fDate);
end;

end.

object DateForm: TDateForm
  Left = 225
  Top = 114
  Width = 260
  Height = 265
  ActiveControl = BtnIncrease
  Caption = 'NewDate'
  Color = clBtnFace
  Font.Charset = ANSI_CHARSET
  Font.Color = clWindowText
  Font.Height = -11
  Font.Name = 'MS Sans Serif'
  Font.Style = []
  OldCreateOrder = True
  OnCreate = FormCreate
  OnDestroy = FormDestroy
  PixelsPerInch = 96
  TextHeight = 13
  object LabelDate: TLabel
    Left = 3
    Top = 16
    Width = 248
    Height = 22
    Alignment = taCenter
    AutoSize = False
    Caption = 'date'
    Font.Charset = ANSI_CHARSET
    Font.Color = clBlack
    Font.Height = -16
    Font.Name = 'Arial'
    Font.Style = [fsBold]
    ParentFont = False
  end
  object BtnIncrease: TButton
    Left = 32
    Top = 64
    Width = 81
    Height = 41
    Caption = '&Increase'
    TabOrder = 0
    OnClick = BtnIncreaseClick
  end
  object BtnDecrease: TButton
    Left = 128
    Top = 64
    Width = 89
    Height = 41
    Caption = '&Decrease'
    TabOrder = 1
    OnClick = BtnDecreaseClick
  end
  object BtnAdd10: TButton
    Left = 32
    Top = 120
    Width = 81
    Height = 41
    Caption = '&Add 10'
    TabOrder = 2
    OnClick = BtnAdd10Click
  end
  object BtnSubtract10: TButton
    Left = 128
    Top = 120
    Width = 89
    Height = 41
    Caption = '&Subtract 10'
    TabOrder = 3
    OnClick = BtnSubtract10Click
  end
  object BtnLeap: TButton
    Left = 32
    Top = 176
    Width = 81
    Height = 41
    Caption = '&Leap Year?'
    TabOrder = 4
    OnClick = BtnLeapClick
  end
  object BtnToday: TButton
    Left = 128
    Top = 176
    Width = 89
    Height = 41
    Caption = '&Today'
    TabOrder = 5
    OnClick = BtnTodayClick
  end
end