NSDate et al woes on iOS 4.2

问题

I believe that NSDate/NSCalendar has a bug or two on iOS 4.2.

[[NSDate date] description]

always prints using GMT, i.e. the local time zone setting is ignored. Has been reported previously, but is included to hopefully better explain the output below.

[calendar ordinalityOfUnit:NSDayCalendarUnit inUnit:NSEraCalendarUnit forDate:dateA]

Doesn't always return the correct value, while this does:

[calendar ordinalityOfUnit:NSDayCalendarUnit inUnit:NSYearCalendarUnit forDate:dateA]

Based on a previous post, I created some test code:

NSDateFormatter* formatter = [[NSDateFormatter alloc] init];
[formatter setDateFormat:@"yyyy-MM-dd HH:mm:ss Z"];  

NSDate* dateA = [formatter dateFromString:@"2010-12-29 11:11:17 +1100"];  
NSDate* dateB = [formatter dateFromString:@"2010-12-29 10:11:17 +1100"];  
NSDate* dateC = [formatter dateFromString:@"2010-12-27 11:11:17 +1100"];  
NSDate* dateD = [formatter dateFromString:@"2010-12-27 10:11:17 +1100"];  
NSLog(@"dateA=%@, %@", dateA, [formatter stringFromDate:dateA]);
NSLog(@"dateB=%@, %@", dateB, [formatter stringFromDate:dateB]);
NSLog(@"dateC=%@, %@", dateC, [formatter stringFromDate:dateC]);
NSLog(@"dateD=%@, %@", dateD, [formatter stringFromDate:dateD]);

NSCalendar* calendar = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
NSLog(@"timezone=%@", [calendar timeZone]);

NSLog(@"A day inUnit:Year=%d", [calendar ordinalityOfUnit:NSDayCalendarUnit inUnit:NSYearCalendarUnit forDate:dateA]);
NSLog(@"B day inUnit:Year=%d", [calendar ordinalityOfUnit:NSDayCalendarUnit inUnit:NSYearCalendarUnit forDate:dateB]);
NSLog(@"C day inUnit:Year=%d", [calendar ordinalityOfUnit:NSDayCalendarUnit inUnit:NSYearCalendarUnit forDate:dateC]);
NSLog(@"D day inUnit:Year=%d", [calendar ordinalityOfUnit:NSDayCalendarUnit inUnit:NSYearCalendarUnit forDate:dateD]);
NSLog(@"A day inUnit:Era =%d", [calendar ordinalityOfUnit:NSDayCalendarUnit inUnit:NSEraCalendarUnit forDate:dateA]);
NSLog(@"B day inUnit:Era =%d", [calendar ordinalityOfUnit:NSDayCalendarUnit inUnit:NSEraCalendarUnit forDate:dateB]);
NSLog(@"C day inUnit:Era =%d", [calendar ordinalityOfUnit:NSDayCalendarUnit inUnit:NSEraCalendarUnit forDate:dateC]);
NSLog(@"D day inUnit:Era =%d", [calendar ordinalityOfUnit:NSDayCalendarUnit inUnit:NSEraCalendarUnit forDate:dateD]);

and got this output:

[33920:207] dateA=2010-12-29 00:11:17 +0000, 2010-12-29 11:11:17 +1100
[33920:207] dateB=2010-12-28 23:11:17 +0000, 2010-12-29 10:11:17 +1100
[33920:207] dateC=2010-12-27 00:11:17 +0000, 2010-12-27 11:11:17 +1100
[33920:207] dateD=2010-12-26 23:11:17 +0000, 2010-12-27 10:11:17 +1100
[33920:207] timezone=Australia/Hobart (GMT+11:00) offset 39600 (Daylight)
[33920:207] A day inUnit:Year=363
[33920:207] B day inUnit:Year=363
[33920:207] C day inUnit:Year=361
[33920:207] D day inUnit:Year=361
[33920:207] A day inUnit:Era =734135
[33920:207] B day inUnit:Era =734134
[33920:207] C day inUnit:Era =734133
[33920:207] D day inUnit:Era =734132

回答1:

I found that by offsetting the date by the time zone offset I get a consistent ordinality.

Taking dateC and dateD from your code:

NSTimeZone *tz = [[NSCalendar autoupdatingCurrentCalendar] timeZone];
NSTimeInterval offset =  [tz secondsFromGMT];

NSDate* dateC = [formatter dateFromString:@"2010-12-27 11:11:17 +1100"];  
NSDate* dateD = [formatter dateFromString:@"2010-12-27 10:11:17 +1100"];  

NSLog(@"dateC=%@, %@", dateC, [formatter stringFromDate:dateC]);
NSLog(@"dateD=%@, %@", dateD, [formatter stringFromDate:dateD]);

dateC = [dateC dateByAddingTimeInterval: offset];
dateD = [dateD dateByAddingTimeInterval: offset];

NSLog(@"C day inUnit:Era =%d", [calendar ordinalityOfUnit:NSDayCalendarUnitinUnit:NSEraCalendarUnit forDate: dateC]);
NSLog(@"D day inUnit:Era =%d", [calendar ordinalityOfUnit:NSDayCalendarUnit inUnit:NSEraCalendarUnit forDate: dateD]);

yields the same ordinality for both.

回答2:

I am seeing the same issue. Doesn't look like the ordinalityOfUnit respects the timezone

来源：https://stackoverflow.com/questions/4550682/nsdate-et-al-woes-on-ios-4-2

标签

nsdate