1   //this code is helpful if you want to write an app to detect whenever
2   //the system time of you PC has changed.
3   unit Unit1;
4   
5   interface
6   
7   uses
8     Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
9     Dialogs, StdCtrls;
10  
11  type
12    TForm1 = class(TForm)
13      Button1: TButton;
14      procedure Button1Click(Sender: TObject);
15    private
16    procedure WMTIMECHANGE(var message: TWMTIMECHANGE);
17          message WM_TIMECHANGE;
18  
19      { Private declarations }
20    public
21      { Public declarations }
22    end;
23  
24  var
25    Form1: TForm1;
26  
27  implementation
28  
29  {$R *.dfm}
30  
31  procedure TForm1.Button1Click(Sender: TObject);
32  begin
33  close;
34  end;
35  
36  procedure TForm1.WMTIMECHANGE(var message: TWMTIMECHANGE);
37  begin
38  ShowMessage('Time changed');
39  end;
40  
41  end.