NSCalendar to get date difference between now and end of year gives a zero month

Question

I'm getting a 0 for the month when I try to get the date difference from now and the end of the year. I'm using a NSCalendar object to get the difference between two NSDate objects.

NSDateComponents *comps = [[NSDateComponents alloc] init];
[comps setYear:2013];
[comps setMonth:0];
[comps setDay:0];

[comps setHour:0];
[comps setMinute:0];
[comps setSecond:0];

NSCalendar *calendar = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
NSDate *newDate = [calendar dateFromComponents:comps];

NSDateComponents *timeDifference = [[NSCalendar currentCalendar] 
    components: NSMonthCalendarUnit | NSDayCalendarUnit | NSHourCalendarUnit | 
                NSMinuteCalendarUnit | NSSecondCalendarUnit  
    fromDate:[NSDate date] toDate:newDate options:0];

int months = timeDifference.month;
int days = timeDifference.day;
if (months>0)
    days+=31;
int hours = timeDifference.hour;
int minutes = timeDifference.minute;
int seconds = timeDifference.second; 

Answer 1

You're trying to calculate number of months, days, etc to year 2013. In NSDateComponents 0 means 'no value', all values that count should be greater than 0. That's why your comps value is considered as 'incomplete', which causes strange output from NSCalendar.

Set month and day in lines 3-4 to 1 fix the issue.