Show your ID before changing the system time

Changing the system time using the Win32 API isn't as easy as it was in the Win16 world. This is because in Windows NT environment you have to get certain security permissions before changing the system time. Here's how to put the Windows security guard to sleep and change the time:

function SetPrivilege(
  sPrivilegeName : string;
  bEnabled : boolean )
    : boolean;
var
  TPPrev,
  TP         : TTokenPrivileges;
  Token      : THandle;
  dwRetLen   : DWord;
begin
  Result := False;

  OpenProcessToken(
    GetCurrentProcess,
    TOKEN_ADJUST_PRIVILEGES
    or TOKEN_QUERY,
    @Token );

  TP.PrivilegeCount := 1;
  if( LookupPrivilegeValue(
        Nil,
        PChar( sPrivilegeName ),
        TP.Privileges[ 0 ].LUID ) )then
  begin
    if( bEnabled )then
    begin
      TP.Privileges[ 0 ].Attributes  :=
        SE_PRIVILEGE_ENABLED;
    end else
    begin
      TP.Privileges[ 0 ].Attributes  :=
        0;
    end;

    dwRetLen := 0;
    Result := AdjustTokenPrivileges(
                Token,
                False,
                TP,
                SizeOf( TPPrev ),
                TPPrev,
                dwRetLen );
  end;

  CloseHandle( Token );
end;

procedure ChangeSystemTime;
var
  st : TSystemTime;
begin
  if( SetPrivilege(
        'SeSystemtimePrivilege',
        True ) )then
  begin
    GetLocalTime( st );

    //
    // change time using st structure
    // for example, to 10:30pm
    //
    st.wHour := 22;
    st.wMinute := 30;

    SetLocalTime( st );
    // or :
    // SetSystemTime( st );

    SetPrivilege(
      'SeSystemtimePrivilege',
      False );
  end;
end;