Conversion from SYSTEMTIME to time_t gives out Time in UTC/GMT

c, c++, mfc, time, visual-c++

Solution

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.

Problem

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.

Original source