从SYSTEMTIME转换为time_t会给出UTC / GMT中的时间

Question

I am trying to convert SYSTEMTIME to time_t through the implementation I found in various forums.

time_t TimeFromSystemTime(const SYSTEMTIME * pTime)
{
    struct tm tm;
    memset(&tm, 0, sizeof(tm));

    tm.tm_year = pTime->wYear - 1900; // EDIT 2 : 1900's Offset as per comment
    tm.tm_mon = pTime->wMonth - 1;
    tm.tm_mday = pTime->wDay;

    tm.tm_hour = pTime->wHour;
    tm.tm_min = pTime->wMinute;
    tm.tm_sec = pTime->wSecond;
    tm.tm_isdst = -1; // Edit 2: Added as per comment

    return mktime(&tm);
}

But to my surprise, the tm is carrying the data corresponds to the local time but the mktime() returns the time_t corresponds to the time in UTC.

Is this the way it works or am I missing anything here?

Thanks for the help in advance !!

EDIT 1: I want to convert the SYSTEMTIME which carries my Local time as the time_t exactly.

I am using this in the VC6 based MFC application.

EDIT 2: Modified Code.

Answer 1

I finally found the Solution from the Windows SDK, through TIME_ZONE_INFORMATION and _timezone

time_t GetLocaleDateTime( time_t ttdateTime) // The time_t from the mktime() is fed here as the Parameter
{
    if(ttdateTime <= 0)
        return 0;

    TIME_ZONE_INFORMATION tzi;

    GetTimeZoneInformation(&tzi); // We can also use the StandardBias of the TIME_ZONE_INFORMATION

    int iTz = -_timezone; // Current Timezone Offset from UTC in Seconds

    iTz = (iTz >  12*3600) ? (iTz - 24*3600) : iTz; // 14  ==> -10
    iTz = (iTz < -11*3600) ? (iTz + 24*3600) : iTz; // -14 ==> 10

    ttdateTime += iTz;

    return ttdateTime;
}

EDIT 1 : Please do add your comments, and also if you see any bugs feel free to comment or edit. Thanks.