type
  TPreciseTime = class(TObject)
  private
    FTimeType    : TTimeType;
    FInitDT      : TDateTime;
    FStart       : int64;
    FFreq        : int64;

    procedure SetTimeType(const Value: TTimeType);
    function GetDateTime: TDateTime;
    function GetDate: TDateTime;
    function GetTime: TDateTime;
  protected
    function InitTime : TDateTime;
  public
    constructor Create(ATimeType : TTimeType);
    property DateTime : TDateTime read GetDateTime;
    property Date : TDateTime read GetDate;
    property Time : TDateTime read GetTime;
    property TimeType : TTimeType read FTimeType write SetTimeType;
  end;

{ TPreciseTime }

constructor TPreciseTime.Create(ATimeType: TTimeType);
begin
  FTimeType := ATimeType;
  InitTime;
end;

function TPreciseTime.GetDate: TDateTime;
begin
  Result := DateOf(DateTime)
end;

function TPreciseTime.GetDateTime: TDateTime;
var _End : int64;
begin
  QueryPerformanceCounter(_End);
  Result := FInitDT + (((_End - FStart) * 1000) div FFreq) / 86400000.0;
end;

function TPreciseTime.GetTime: TDateTime;
begin
  Result := TimeOf(DateTime);
end;

function TPreciseTime.InitTime: TDateTime;
begin
  QueryPerformanceFrequency(FFreq);
  FInitDT := TimeUnit.GetDateTime(FTimeType);
  QueryPerformanceCounter(FStart);

  Assert(FStart <> 0, EPrecisionTimeInitTimeError);
  Result := FInitDT;
end;

procedure TPreciseTime.SetTimeType(const Value: TTimeType);
begin
  if FTimeType <> Value then begin
    FTimeType := Value;
    InitTime;
  end;
end;