NSCalendar *currentCalendar = [NSCalendar currentCalendar];
NSDate *today = [NSDate date];
NSInteger dc = [currentCalendar  ordinalityOfUnit:NSDayCalendarUnit
                                                  inUnit:NSYearCalendarUnit
                                                 forDate:today];

//create calendar
NSCalendar *calendar = [NSCalendar currentCalendar];

//set calendar time zone
[calendar setTimeZone:[NSTimeZone timeZoneWithAbbreviation:@"UTC"]];

//gather date components
NSDateComponents *components = [calendar components:NSDayCalendarUnit fromDate:[NSDate date]];

//gather time components
NSInteger day = [components day];

NSCalendar *cal = [NSCalendar currentCalendar];
NSDateFormatter *df = [[NSDateFormatter alloc] init];

[df setCalendar:cal];
[df setDateFormat:@"DDD"];    // D specifier used for day of year
NSString *dayOfYearString = [df stringFromDate:someDate];  // you choose 'someDate'

NSLog(@"The day is: %@", dayOfYearString);

// create your NSDate and NSCalendar objects
NSDate *today = [NSDate date];
NSDate *referenceDate;
NSCalendar *calendar = [NSCalendar currentCalendar];

// get today's date components
NSDateComponents *components = [calendar components:NSDayCalendarUnit | NSMonthCalendarUnit | NSYearCalendarUnit fromDate:today];

// changing the date components to the 31nd of December of last year
components.day = 31;
components.month = 12;
components.year--;

// store these components in your date object
referenceDate = [calendar dateFromComponents:components];

// get the number of days from that date until today
components = [calendar components:NSDayCalendarUnit fromDate:referenceDate toDate:[NSDate date] options:0];
NSInteger days = components.day;