ios6 - 如何设置时区（UTC）UIDatePicker？

Question

我想将时区从 (-12:00) - (+12:00) 设置为 (-23:45) -(+23:45)

+ (NSArray *)timeZoneList {
  NSMutable *list = [[NSMustableArry alloc]init];
  for(int n = -(23 * 60+45); n<= 23*60+45; n+=15; {
    NSString * timeZoneName = @"UTC ";
    NSString *sign;
    if (n==0) sign = @"+-";
    else if(n<0) sign = @"-";
    else sign = @"+";
    timeZoneName = [timeZoneName stringByAppendinfFormat:@"%@ %.2d:%.2d",sign,abs(n/60),abs(n%60)];

    NSTimeZone *timeZone = [NSTimeZone timeZoneForSecondsFromGMT:n*60];
    [list addObject:[NSArray arryWithObjects:timeZoneName,timeZone,nil]];
  }
  return [list copy];
}

我在 (-18:15) - (+18:15) 上面发现了一个问题。

我能做些什么？请指教。