相同字符串格式的 NSDateFormatter 结果不一致

Question

为什么这种转换有时有效，有时却无效？ 当它不起作用时，eDate 为空。原始转换失败..但工作和转换之间的格式非工作日期字符串看起来相同。 我尝试在两个格式化程序中为 dd 而不是 d 添加额外的“d”。这并没有解决问题

    NSDateFormatter *dateFormatter = [[[NSDateFormatter alloc]init]autorelease];        
[dateFormatter setDateFormat:@"EEE MMM d hh:mm:ss Z yyyy"];
NSDate *eDate = [dateFormatter dateFromString:[responceDictionary objectForKey: @"created_at"]];
NSLog(@"original string: %@", [responceDictionary objectForKey: @"created_at"]);

NSDateFormatter *shortFormatter = [[[NSDateFormatter alloc] init] autorelease];
[shortFormatter setDateFormat:@"EEE MMM d hh:mm"];
 NSString *todayString = [shortFormatter stringFromDate:eDate];
 NSLog(@"todayString: %@", todayString);


    2011-05-12 11:01:52.768 Application[1707:207] original string: Wed May 11 19:30:57   +0000 2011
2011-05-12 11:01:52.769 Application[1707:207] todayString: (null)
2011-05-12 11:01:52.770 Application[1707:207] original string: Tue May 10 18:45:01 +0000     2011
2011-05-12 11:01:52.770 Application[1707:207] todayString: (null)
2011-05-12 11:01:52.771 Application[1707:207] original string: Tue May 10 02:24:48 +0000     2011
2011-05-12 11:01:52.771 Application[1707:207] todayString: Mon May 9 09:24
2011-05-12 11:01:52.772 Application[1707:207] original string: Tue May 10 01:05:05 +0000     2011
2011-05-12 11:01:52.772 Application[1707:207] todayString: Mon May 9 08:05
2011-05-12 11:01:52.773 Application[1707:207] original string: Mon May 09 17:38:14 +0000     2011
2011-05-12 11:01:52.774 Application[1707:207] todayString: (null)
2011-05-12 11:01:52.774 Application[1707:207] original string: Fri May 06 12:36:30 +0000     2011
2011-05-12 11:01:52.775 Application[1707:207] todayString: Thu May 5 07:36
2011-05-12 11:01:52.775 Application[1707:207] original string: Fri May 06 12:08:58 +0000     2011
2011-05-12 11:01:52.776 Application[1707:207] todayString: Thu May 5 07:08
2011-05-12 11:01:52.777 Application[1707:207] original string: Fri May 06 11:56:44 +0000     2011
2011-05-12 11:01:52.778 Application[1707:207] todayString: Fri May 6 06:56
2011-05-12 11:01:52.778 Application[1707:207] original string: Thu May 05 22:17:48 +0000     2011
2011-05-12 11:01:52.779 Application[1707:207] todayString: (null)

Answer 1

尝试在日期格式中使用 HH 而不是 hh 。

unicode 日期格式规范 规定 h表示 12 (1-12) 小时格式的小时，H 表示 24 (0-23) 小时格式的小时。

NSDateFormatter 无法创建日期，因为 22 （如上一个示例）超出了 12 小时的限制。