NSDate：5是坑啊啊！

 NSDateFormatter \*dateFormatter = \[\[NSDateFormatter alloc\] init\];

 \[dateFormatter setDateFormat:@"yyyy/MM/dd hh:mm:ss"\];

 NSLog(@"0:%@",\[dateFormatter stringFromDate:\[NSDate date\]\]);

 \[dateFormatter setTimeZone:\[NSTimeZone systemTimeZone\]\];

 NSLog(@"1:%@",\[dateFormatter stringFromDate:\[NSDate date\]\]);

 \[dateFormatter setTimeZone:\[NSTimeZone defaultTimeZone\]\];

 NSLog(@"2:%@",\[dateFormatter stringFromDate:\[NSDate date\]\]);

 \[dateFormatter setTimeZone:\[NSTimeZone localTimeZone\]\];

 NSLog(@"3:%@",\[dateFormatter stringFromDate:\[NSDate date\]\]);

 \[dateFormatter setTimeZone:\[NSTimeZone timeZoneWithName:@"Asia/Shanghai"\]\];

 NSLog(@"4:%@",\[dateFormatter stringFromDate:\[NSDate date\]\]);

 \[dateFormatter setTimeZone:\[\[NSTimeZone alloc\] initWithName:@"Asia/Shanghai"\]\];

 NSLog(@"5:%@",\[dateFormatter dateFromString:\[dateFormatter stringFromDate:\[NSDate date\]\]\]);

0:2015/02/03 09:41:14

1:2015/02/03 09:41:14

2:2015/02/03 09:41:14

3:2015/02/03 09:41:14

4:2015/02/03 09:41:14

5:2015-02-03 01:41:14 +0000

附带NSDate详情链接：http://www.cnblogs.com/ios-wmm/archive/2013/04/21/3034204.html