delphi - GetDateFileModified 夏令时

Question

function DateTimeToFileTime(FileTime: TDateTime): TFileTime;
var
  LocalFileTime, Ft: TFileTime;
  SystemTime: TSystemTime;
begin
  Result.dwLowDateTime := 0;
  Result.dwHighDateTime := 0;
  DateTimeToSystemTime(FileTime, SystemTime);
  SystemTimeToFileTime(SystemTime, LocalFileTime);
  LocalFileTimeToFileTime(LocalFileTime, Ft);
  Result := Ft;
end;

function ExtractShortDate(ATimeIn: TDateTime): string;
// Convert DateTime to short date string
begin
  Result := FormatDateTime('mm/dd/yyyy', ATimeIn);
end;

function ExtractTime(ATimeIn: TDateTime): string;
// Convert DateTime to am/pm time string
begin
  Result := FormatDateTime('hh:mm AM/PM', ATimeIn);
end;

function GetDateFileModified(AFileName: string): string;
// Return the file modified date as a string in local time
var
  SR: TSearchRec;
  UTCTime: Windows.TFileTime;
  GMTST: Windows.TSystemTime;
  LocalST: Windows.TSystemTime;
  ModifyDT: TDateTime;
  TZ: Windows._TIME_ZONE_INFORMATION;
begin
  Result := '';
  if FindFirst(AFileName, faAnyFile, SR) = 0 then
  begin
    UTCTime := SR.FindData.ftLastWriteTime;
    if FileTimeToSystemTime(UTCTime, GMTST) then
    begin
       // Get Timezone Information
      if GetTimeZoneInformation(TZ) <> 0 then
        if SystemTimeToTzSpecificLocalTime(@TZ, GMTST, LocalST) then
        begin
          ModifyDT := SystemTimeToDateTime(LocalST);
          Result := ExtractShortDate(ModifyDT) + ' ' + ExtractTime(ModifyDT);
        end
        else
        begin
          TaskMessageDlg('Unable To Convert Time', 'Unable to convert SystemTime To LocalTime',
            mtInformation, [mbOk], 0);
          Result := '';
          exit;
        end;
    end
    else
    begin
      TaskMessageDlg('Unable To Convert Time', 'Unable to convert FileTime To SystemTime',
        mtInformation, [mbOk], 0);
      Result := '';
      exit;
    end;
  end
  else
    TaskMessageDlg('File Not Found', ExtractFileName(AFileName) + ' does not exist.',
      mtInformation, [mbOk], 0);
  FindClose(SR);
end;

发布的原始代码未返回正确的时间。原始代码已替换为工作代码，以便其他人可能会发现这很有用。

更新:由于所有协助，代码现在提供了正确的时间。

Answer 1

MSDN 文档中针对 FileTimeToLocalFileTime 突出显示了该问题:

FileTimeToLocalFileTime uses the current settings for the time zone and daylight saving time. Therefore, if it is daylight saving time, this function will take daylight saving time into account, even if the time you are converting is in standard time. You can use the following sequence of functions as an alternative.

FileTimeToSystemTime / SystemTimeToTzSpecificLocalTime / SystemTimeToFileTime

每当您在夏令时更改后查看更改之前创建的文件时，您都需要使用指定的三个函数(但是当您和文件创建都位于文件的同一侧时，此方法当然也适用)夏令时更改)。