FILETIMEからDATEへの変換

    static HRESULT FileTimeToVariantTime(const FILETIME& fileTime, DATE* pDate)

    {

        if (pDate == NULL)

        {

            return E_POINTER;

        }

        SYSTEMTIME systemTime;

        BOOL br = ::FileTimeToSystemTime(&fileTime, &systemTime);

        if (br == 0)

        {

            DWORD dwError = ::GetLastError();

            return HRESULT_FROM_WIN32(dwError);

        }

        int nr = ::SystemTimeToVariantTime(&systemTime, pDate);

        if (nr == 0)

        {

            DWORD dwError = ::GetLastError();

            return HRESULT_FROM_WIN32(dwError);

        }

        return S_OK;

    }

    static HRESULT VariantTimeToFileTime(const DATE& date, FILETIME* pFileTime)

    {

        if (pFileTime == NULL)

        {

            return E_POINTER;

        }

        SYSTEMTIME systemTime;

        int nr = ::VariantTimeToSystemTime(date, &systemTime);

        if (nr == 0)

        {

            DWORD dwError = ::GetLastError();

            return HRESULT_FROM_WIN32(dwError);

        }

        FILETIME ft;

        BOOL  br = ::SystemTimeToFileTime(&systemTime, &ft);

        if (br)

            br = ::LocalFileTimeToFileTime(&ft, pFileTime);

        if (br == 0)

        {

            DWORD dwError = ::GetLastError();

            return HRESULT_FROM_WIN32(dwError);

        }

        return S_OK;

    }