if( _putenv( "TZ=EST5EDT" ) == -1 )
{
printf( "Unable to set TZ\n" );
exit( 1 );
}
else
{
_tzset();
printf( "_daylight = %d\n", _daylight );
printf( "_timezone = %ld\n", _timezone );
printf( "_tzname[0] = %s\n", _tzname[0] );
}
FROM MSDN
Read between the lines