How do you get info for an arbitrary time zone in Windows?

Question

Ideally, what I\'d like to be able to do is take the name of a time zone and ask Windows for its corresponding time zone info (offset from UTC, DST offset, dates for DST swi

Answer 1

Here is an example without the registry. The timezone information depends on the year, so I added a parameter to hold that.

TIME_ZONE_INFORMATION GmtTimezone( const wstring& name, SYSTEMTIME utc )
{
    DYNAMIC_TIME_ZONE_INFORMATION dynamicTimezone = {};
    DWORD result=0;
    for( DWORD i = 0; result!=ERROR_NO_MORE_ITEMS; ++i )
    {
        result = ::EnumDynamicTimeZoneInformation( i, &dynamicTimezone );
        if( result==ERROR_SUCCESS && name==dynamicTimezone.StandardName )
            break;
    }
    if( result!=ERROR_SUCCESS )
        throw L"Could not find timezone "+name;

    TIME_ZONE_INFORMATION tz;
    if( !GetTimeZoneInformationForYear(static_cast(utc.wYear), &dynamicTimezone, &tz) )
        throw "GetTimeZoneInformationForYear failed"+std::to_string(GetLastError());
    return tz;
    //SYSTEMTIME localTime;
    //SystemTimeToTzSpecificLocalTime( &tz, &utc, &localTime );
    //auto offsetHours = localTime.wHour-utc.wHour;
}