oc时间从美国时间改到中国时间

   _formatter = [[NSDateFormatter alloc]init];
    NSString *formatString = [NSDateFormatter dateFormatFromTemplate:@"HH:mm" options:0
                                                              locale:[NSLocale currentLocale]];
   
    [_formatter setTimeZone:[NSTimeZone timeZoneForSecondsFromGMT:8]];
   
    [_formatter setDateFormat:formatString];