I am using the following NSCalendar
method to get the number of days in a calendar year:
NSRange range = [gregorian rangeOfUnit:NSDayCalendarUnit
inUnit:NSYearCalendarUnit
forDate:date];
I am expecting a range.length
return value of type NSRange
which is 365 or 366 (days).
However, this code returns a range.length
of 31
for a date value of 2005-06-06
.
What is wrong with my code?
This is the full code snippet:
NSCalendar *gregorian = [[NSCalendar alloc]
initWithCalendarIdentifier:NSGregorianCalendar];
[subArray enumerateObjectsUsingBlock:
^(NSDate *date, NSUInteger idx, BOOL *stop) {
NSUInteger numberOfDays = [gregorian ordinalityOfUnit:NSDayCalendarUnit
inUnit:NSYearCalendarUnit forDate:date];
}];
This calculates the number of days of a year of a given date:
NSDate *someDate = [NSDate date];
NSDate *beginningOfYear;
NSTimeInterval lengthOfYear;
NSCalendar *gregorian = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
[gregorian rangeOfUnit:NSYearCalendarUnit
startDate:&beginningOfYear
interval:&lengthOfYear
forDate:someDate];
NSDate *nextYear = [beginningOfYear dateByAddingTimeInterval:lengthOfYear];
NSInteger startDay = [gregorian ordinalityOfUnit:NSDayCalendarUnit
inUnit:NSEraCalendarUnit
forDate:beginningOfYear];
NSInteger endDay = [gregorian ordinalityOfUnit:NSDayCalendarUnit
inUnit:NSEraCalendarUnit
forDate:nextYear];
NSInteger daysInYear = endDay - startDay;
Sad caveat: This does not work correctly for year 1582.
The year 1582, the year when Gregor introduced the currently widespread used calendar, needed a fix to align solar with calendar years. So they went with the pragmatic solution: They just dropped October 5-14. (They were not crazy enough to change weekdays, too). As a result the year 1582 only has 355 days.
Addendum: The code above only works correctly for years after 1582. It returns 365 days for the year 1500, for example, even though this year was a leap year in the then used julian calendar. The gregorian calendar starts at October 15, 1582. Computations made on the gregorian calendar are just not defined before that date. So in this way Apple's implementation is correct. I'm not aware of a correct implementation for years before 1583 on Cocoa.
Here's a relatively clean version. It's a category on NSCalendar.
- (NSInteger) daysInYear:(NSInteger) year {
NSDateComponents *dateComponents = [[NSDateComponents alloc] init];
dateComponents.year = year;
dateComponents.month = dateComponents.day = 1;
NSDate *firstOfYear = [self dateFromComponents:dateComponents];
dateComponents.year = year + 1;
NSDate *firstOfFollowingYear = [self dateFromComponents:dateComponents];
return [[self components:NSDayCalendarUnit
fromDate:firstOfYear
toDate:firstOfFollowingYear
options:0] day];
}
Thanks to AKV for pointing out that -components:fromDate:toDate:options
will work in this case.
This doesn't seem to work for 1582 or prior, which per Nikolai Ruhe's answer is because Gregorian calendar calculations simply aren't defined prior to then.
What about finding number of days in a given year as: Although this is not the relative solution for the question.
-(NSInteger)daysBetweenTwoDates:(NSDate *)fromDateTime andDate:(NSDate *)toDateTime{
NSDate *fromDate;
NSDate *toDate;
NSCalendar *calendar = [NSCalendar currentCalendar];
[calendar rangeOfUnit:NSDayCalendarUnit startDate:&fromDate interval:NULL forDate:fromDateTime];
[calendar rangeOfUnit:NSDayCalendarUnit startDate:&toDate interval:NULL forDate:toDateTime];
NSDateComponents *difference = [calendar components:NSDayCalendarUnit fromDate:fromDate toDate:toDate options:0];
return [difference day];
}
-(void)someMethod {
NSString *yourYear=@"2012";
NSDate *date1 = [NSDate dateWithString:[NSString stringWithFormat:@"%@-01-01 00:00:00 +0000",yourYear]];
NSDate *date2 = [NSDate dateWithString:[NSString stringWithFormat:@"%@-12-31 00:00:00 +0000",yourYear]];
NSInteger numberOfDays=[self daysBetweenTwoDates:date1 andDate:date2];
NSLog(@"There are %ld days in between the two dates.", numberOfDays);
}
Edit:
As dateWithString: is deprecated, you can use
NSDateFormatter *dateFormatter=[[NSDateFormatter alloc] init];
[dateFormatter dateFormat]=@"dd-MM-yyyy";
NSDate *date=[dateFormatter dateFromString:dateString];
to form date1
and date2
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